occupational choices: economic determinants of land...
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Occupational Choices:
Economic Determinants of Land Invasions∗
F. Daniel Hidalgo†
Suresh Naidu
Simeon Nichter
Neal Richardson
April 30, 2007
Abstract
This study estimates the effect of economic conditions on redistributive conflict. Weexamine land invasions in Brazil using a panel dataset with over 50,000 municipality-year observations. Adverse economic shocks, instrumented by rainfall, cause the ruralpoor to invade and occupy large landholdings. This effect exhibits substantial hetero-geneity by land inequality and land tenure systems. In highly unequal municipalities,negative income shocks cause twice as many land invasions than in municipalities withaverage land inequality. We find no further evidence of heterogeneity on other observ-able variables. Cross-sectional regressions confirm the importance of land inequality inexplaining redistributive conflict.
Keywords: land conflict, inequality, redistribution, rainfall, political economy, devel-opment, social movement, collective actionJEL codes: D74, Q15, D3, O17, P16
∗The authors would like to thank Raymundo Nonato Borges, David Collier, Bernardo Mancano Fernan-des, Stephen Haber, Steven Helfand, Rodolfo Hoffmann, Ted Miguel, Bernardo Mueller, Jim Powell, DavidSamuels, Edelcio Vigna and participants in the Development Economics Seminar and the Latin AmericanPolitics Seminar at the University of California, Berkeley. A previous version of this paper was presented atthe XXVI International Congress of the Latin American Studies Association, San Juan, PR (March 15-18,2006). The authors recognize support of the National Science Foundation Graduate Research FellowshipProgram, the Jacob K. Javits Fellowship Program, and the UC Berkeley Center for Latin American Studies.
†Hidalgo, Nichter, and Richardson: Department of Political Science, University of California, Berke-ley; Naidu: Department of Economics, University of California, Berkeley. Authors’ email addresses:[email protected]; [email protected]; [email protected]; [email protected].
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1 Introduction
Conflict over land is endemic to many rural economies. In environments marked by a highly
skewed distribution of property, incomplete land and credit markets, poorly or unevenly
enforced property rights, and weak political institutions, agents often resort to extralegal
means to improve their economic positions. The poor frequently invade private properties
and occupy them until either forcibly expelled or granted official titles. Land occupations
are prevalent in Brazil [CPT 1988-2004], South Africa [Simmons 2001], Venezuela [Econo-
mist 2001] and many other countries. How do economic conditions affect this redistributive
conflict?
This paper explores this question using a rich municipal-level dataset of 5,299 land
invasions from 1988 to 2004 in Brazil. Employing exogenous variation in income generated
by rainfall, this study finds that adverse economic shocks cause the rural poor to occupy
large landholdings. This effect is magnified by land inequality. In highly unequal munici-
palities, negative income shocks cause twice as many land invasions than in municipalities
with average land inequality. When using a measure of land polarization, which captures
the degree of bimodality of the land distribution, the effect is even stronger. Moreover,
cross-sectional specifications confirm the importance of land inequality in explaining redis-
tributive conflict.
In addition to heterogeneity by land inequality, we find that income shocks cause
significantly more land invasions in municipalities with a greater proportion of land under
fixed-rent contracts. We find no evidence of heterogeneity on other political and socioeco-
nomic variables. The impact of income shocks does not differ significantly across levels of
political competition, sharecropping, police expenditures, or social welfare spending. Our
findings provide new evidence on the underexplored relationship between inequality and
redistributive conflict.
2
While several papers have identified a causal relationship between income and con-
flict, none have found that this relationship varies by economic institutions or the distri-
bution of assets. Our paper is the first to show that the effect of income shocks exhibits
heterogeneity in ways consistent with qualitative evidence and economic theories of conflict.
Previous papers have been unable to examine many plausible sources of potential hetero-
geneity because of data limitations [Miguel, Satyanath, and Sergenti 2004; Do and Iyer
2006]. The rich nature of our data, however, allows us to test for a large set of interactions.
Importantly, the motivations behind the conflict we examine are explicitly redistributive,
while other work primarily considers civil wars, which are fought for a variety of economic
and non-economic reasons.
This paper also contributes to a longstanding debate in the fields of political science
and sociology: when do the rural poor become politically active? Studies of political change
have long explored this question because of the important historical role of agrarian class
conflict in institutional transitions [Moore 1966; Huntington 1968; Skocpol 1979; Luebbert
1991]. Much of this literature studies poverty, inequality and rural class conflict [e.g., Scott
1976; Popkin 1976], and some suggest that different systems of land tenure foster or inhibit
peasant mobilization. The theories, however, often point in contradictory directions. For
example, Stinchcombe [1961] and Paige [1975] argue that small landowners are typically
conservative, generally supporting modest reform movements, while Wolf [1969] claims that
they are more likely to be radicalized. The capacity for sharecroppers to mobilize is also
widely debated among these authors. These conclusions, however, are generally based on
in-depth case studies; few studies are quantitative1 and none attempt to identify the causal
impact of income shocks.
The paper is organized as follows. In Section 2, we present a brief overview of land
1But see Paige [1975] and Markoff [1996].
3
conflict in Brazil. Section 4 explains data sources. Our identification strategy is discussed
in Section 5. Section 6 presents basic results and robustness checks. Section 7 examines
heterogeneity across land inequality, land tenure, and other observable variables. Section 8
confirms the importance of land inequality in cross-municipality specifications, and Section
9 concludes.
2 Overall Context
According to the Food and Agricultural Organization of the United Nations, Brazil has
the eighth-most unequal distribution of land in the world [FAO 2005]. The concentration
of property in Brazil is so skewed that the largest 3.5 percent of landholdings represent
56 percent of total agricultural land. Land inequality has long persisted in Brazil.2 The
Gini coefficient of land inequality remained stable between 1967 and 1998, measuring 0.84
in both the beginning and end of the period. And while some regional differences exist,
with the North, Northeast and Center-West relatively more unequal than the South and
Southeast, land inequality in all regions is high when compared internationally [Hoffmann
1998; Griffin, Khan, and Ickowitz 2002].
Efforts to reduce Brazil’s land inequality have been hamstrung by political con-
straints. During the presidency of Getulio Vargas (1930-45), proposals for land reform
emerged but were quickly sidelined because Vargas relied on continued support from landed
elites [Morissawa 2001, p. 81]. In the early 1960s, President Joao Goulart initiated modest
land reform measures but was soon ousted by the military coup of 1964. Land reform stag-
nated during the twenty-year military dictatorship. Although President Castelo Branco
2High land inequality dates back to the initial European partitioning of the New World. During thecolonial period, the Portuguese monarchy divided Brazil’s territory into twelve captaincies. By bestowingthese massive properties to individuals, the Portuguese established a land structure based on latifundios,or large rural landholdings [Bethell 1987].
4
approved the Brazilian Land Statute (1964), which introduced the “social function” of
land as a legal concept and identified landholding categories eligible for expropriation, the
section relating to land reform was “virtually abandoned” due to immense pressure from
landed elites [Morissawa 2001, p. 99]. The authoritarian regime expropriated only eight
properties per year on average, and instead attempted to placate rural peasants through
colonization projects, which typically entailed resettlements to government land in the
Amazon [Alston, Libecap, and Mueller 1999, pp. 135-6].
Even since Brazil’s transition to democracy in 1985, land reform has been limited.
In 1985, President Jose Sarney launched the National Agrarian Reform Plan, which ambi-
tiously established a goal of resettling 1.4 million families during the following five years.
However, INCRA, the national agrarian reform agency, only resettled 90,000 families dur-
ing this period [Cardoso 1997, p. 24].3 Then, land reform virtually stopped during the
Collor de Mello presidency (1990-92). Afterwards, President Itamar Franco (1992-94) ini-
tiated an emergency land reform program aiming to redistribute land to 80,000 families,
but reached only 23,000 families [Cardoso 1997, p. 25].
Amidst limited formal land reform, many poor Brazilians have invaded private es-
tates and public lands, squatting in an attempt to appropriate land. As shown in Figure 1,
over 660,000 families—more than 3 million individuals—participated in land invasions in
the Brazilian countryside between 1988 and 2004 [CPT 2004]. By invading large landown-
ers’ property, poor Brazilians have placed the issue of land redistribution on the national
political agenda, pressuring the government to expropriate land. 4 Due in large part to
3INCRA is the Instituto Nacional de Colonizacao e Reforma Agraria (National Institute of Colonizationand Land Reform).
4In part due to such invasions, numerous surveys over the past twenty years reveal the overwhelmingpopularity of formal land reform in Brazil. For example, a 1987 survey found that 83 percent of respondentssupported “expropriating large properties that do not fulfill their social function” [Machado, Magri, andMasagcao 1986, p. 14]. More recently, a national IBOPE poll in 1998 found that 80 percent of respondentsfavored formal land reform.
5
these land invasions, land reform trebled under Fernando Henrique Cardoso (1995-2002),
reaching nearly 260,000 families during his presidency [INCRA 2005].
Land invasions (also termed “land occupations” in Brazil) are large undertakings,
each involving an average of 156 families. Because the land-poor face considerable obstacles
while invading land, coordination of their efforts is important. Consequently, many land
occupations are facilitated by social activists, who help to plan invasions and to assist
families while they squat on occupied properties. Activists affiliated with the Landless
Workers Movement (Movimento dos Trabalhadores Rurais Sem Terra – MST) or other
social groups identify rural properties that are most likely to be expropriated by the federal
government following an invasion, such as underutilized land that does not fulfill its “social
function” (de Janvry et al 1998: 15). Once a target property is identified, activists help
participants to gather food and materials for housing, arrange buses and cars, and develop
secret plans for invasions [Paiero and Damatto 1996, pp. 31-40](Ondetti 2002: 70).
Once a land invasion occurs, the immediate aftermath is extremely tense and fre-
quently violent. Landowners often seek to end invasions by both extralegal and legal
means, simultaneously firing bullets and filing charges. Violence is common—in 2003 alone,
55 land invaders were killed, 73 were physically attacked, and 155 received death threats
[CPT 2003]. To eject squatters, landowners often hire private militias, and may also ob-
tain expulsion orders from local judges enforceable by the military police (de Janvry et al
1998: 16). If the land invaders manage to remain on the property, the national land reform
agency (INCRA) may recognize their claim if it deems the occupied land is “nonproduc-
tive.”5 Given a complicated legal framework, the various legal proceedings involved in a
5If the national land reform agency (INCRA) determines that the occupied land is “productive,” then noexpropriation is legally possible. Otherwise, INCRA may recognize the land invaders’ claim by estimatingthe value of the land and offering a sum to the owner in exchange for expropriation. In some cases,government officials bargain with participants, offering property on government-owned land in exchange fordismantling camps (Ondetti 2002: 71).
6
land occupation take between six months and six years before land is officially expropriated
on behalf of squatters[Wolford 2001]. According to 1996 survey of all registered occupants
of invaded land, 57 percent had begun the official procedures to acquire a land title, while
only 5.6 percent had actually received it (Viero Schmidt et al 1998: 122). With their ex-
tensive experience in pressuring the government to expropriate land, social activists such
as those within the MST help participants to negotiate with the government and navigate
the legal system [Medeiros 2003, p. 52].6
Given the challenges involved in invading land, much literature in political science
and sociology emphasizes the role of the MST and other organizations in mobilizing the
poor to invade properties. Officially founded in 1984, the MST quickly became Latin
America’s largest social movement, and assisted 57 percent of all families squatting on
land in Brazil between 1996 and 1999 [Comparato 2003, p. 104]. While the activities of the
MST and other social groups clearly play an important role in land invasions, they offer
an incomplete explanation for when and where land invasions occur. As Figure 2 shows,
the prevalence of land invasions varies greatly across municipalities in Brazil. This study
explores the extent to which economic conditions help to explain when and where the rural
poor choose to invade land.
Qualitative research on land conflict in Brazil suggest the importance of transitory
income shocks and the concentration of landownership. For example, Wolford [2004] offers
a detailed case study of Agua Preta, a municipality with high land inequality (land Gini
= 0.935) in the northeastern state of Pernambuco. In the early 1990s, sugar plantation
workers faced a substantial income shock due to drought, declines in international sugar
prices, and cuts in government subsidies. As Wolford explains, landless workers became
6For example, the MST often provides technical assistance and training, often in exchange for politicalsupport and help in carrying out more occupations [Wolford 2004].
7
easier to mobilize for land invasions as wage earnings from sugar plantations fell.7 Case
studies by other authors [Palmeira and Leite 1998; Medeiros 2003] similarly emphasize the
effect of economic conditions on land invasions.
3 Theoretical Mechanisms
In this section, we sketch a simple model that generates predictions consistent with our
empirical results and relate it to the literature on the political economy of redistribution
and the theoretical literature on conflict. A number of studies have found an effect of
income on conflict with two mechanisms stressed in the literature. The first is a straight-
forward opportunity cost effect, where negative productivity shocks raise the return to
non-productive appropriative activities. However, few studies have examined how this
effect varies depending on economic institutions or asset distribution.
Another channel some authors have mentioned is that transitory shocks weaken the
governments’ ability to deploy resources that deter conflict. This is unlikely to obtain in
Brazil, as local governments are able to appeal to state and federal repression in order to
deter land occupations that occur in response to a local shock.
Whereas the predicted effect of income shocks on conflict is relatively straightfor-
ward, the relationship between inequality and conflict is more ambiguous. At first glance,
the link between land inequality and land invasions may appear obvious. High land in-
equality concentrates property in relatively few landholdings, so the returns to invading the
largest properties increase. In addition, high land inequality typically is associated with a
higher percentage of the population that is land-poor, which may heighten sensitivity to
7Our data for this municipality corroborate Wolford’s ethnography. In 1993, Agua Preta experienceda dramatic decline in rainfall (1.95 standard units), and crop yields fell as a result. The municipalityexperienced a land invasion that year—its first in the 1988-2004 period—as well as another in the followingyear.
8
economic shocks and thus increase land invasions. High inequality may also make political
institutions less representative [Engerman and Sokoloff 2001], thereby leading the poor to
resort to extralegal action for land redistribution.
Using cross-country regressions, scholars have suggested a positive association of
inequality with political conflict but do not establish causality [Alesina and Perotti 1996;
Keefer and Knack 2002]. However, much of the literature on this topic assumes that re-
distribution is channelled through formal political institutions. We instead highlight a
mechanism where it occurs through decentralized extralegal conflict [Grossman 1994]. In
addition, while scholars frequently emphasize how redistributive pressures can undermine
economic growth [Alesina and Rodrik 1994; Persson and Tabellini 1993], our findings pro-
vide evidence in the other causal direction: contractionary periods can increase some forms
of redistributive pressures.
However, numerous scholars [e.g., Grossman and Kim 1995; Esteban and Ray 1999;
Acemoglu and Robinson 2001] argue that the relationship between inequality and redis-
tributive conflict is nonmonotonic. For example, Acemoglu and Robinson [2006] argue
that in situations with extremely high asset inequality, the rich may be more willing to
expend resources on repression in order to deter revolution. Moreover, it may be easier for
a smaller landholding class to overcome the collective action problem of contributing to
the protection of private property [Esteban and Ray 2002]. Hence, areas with the highest
levels of land inequality may well experience less conflict.
Given that we are examining transitory productivity shocks, one might expect
that the effect of negative income shocks on conflict depends on the institutions that
allocate risk. The development of insurance or credit markets would give agents the ability
to smooth the effects of a negative shock, and should reduce the impact of a negative
productivity shock on land invasions. In addition, agricultural contracts, which allocate risk
9
between land-owners and tenants or workers, may determine how a shock to agricultural
productivity affects the propensity of the landless to engage in invasions. We would expect
fixed-rent contracts, which have the tenant bearing the full impact of shocks, to generate
the most land invasions in response to a transitory productivity shock.
3.1 A Simple Model
In this section we develop a simple model describing that formalizes our main comparative
statics. Rather than developing all the mechanisms described above, we focus on those that
are salient empirically in our data. Consider the decision of a potential land invader, with
labor endowment L and initial land endowment TL. There exists a target landholding that
yields TH − TL > 0 additional units of land. The occupier has preferences given by:
E
∞∑
t=0
βtct (1)
The production function is given by:
F (T, L) = AF (T, L) + rT if T > T ∗ (2)
F (T, L) = rT if T ≤ T ∗ (3)
We assume that TL < T ∗ < TH , so that the land poor have to work for the rich.
After they get their owne land, they cultivate it themselves.
Invaders have to choose between working and engaging in an invasion. The proba-
bility of an invasion succeeding is given by G(Lc). We assume G is concave and increasing.
At is an i.i.d. productivity shock, for our purposes this can be rainfall. The returns to
work depend on the contract offered. Following Braverman and Stiglitz(1974), we model
10
an agricultural contract as consisting of a fixed up-front payment R and a fraction of the
ex-post output α. α = 1 corresponds to a fixed rent contract, while α = 0 is a wage-labor
contract.
For this section, we assume α and R are fixed exogenously, due to local norms(e.g.
as in Burke and Young 2002). Thus, the ex-post returns for the poor working are given by
αAtF (L − Lc, TH) − R + rTL. After the invaders get land, their returns from farming are
given by AtF (L − Lc, TH)
Thus expressing the agent’s problem recursively, the agent faces a problem of choos-
ing L conditional on TL and TH to maximize the pair of equations given by:
V (TL|At) = maxLc(αAtF (L − Lc, TH) − R + rTL + βE[(G(Lc)V (TH) + (1 − G(Lc))V (TL))] (4)
V (TH |At) = maxLc(AtF (L − Lc, TH) + βE[V (TH)]) (5)
The second Bellman equation readily gives:
V (TH |At) =1
1 − βAtF (L, TH) (6)
Thus the agent allocates all labor to production after she has secured enough land to en-
gage in own production.
The first-order condition for L∗c , the amount of appropriative labor exerted by the
agent in the land poor state is:
αAtFL(L − L∗c , TH) + βg(L∗
c)E[V (TH) − V (TL))] = 0 (7)
11
Simple calculations and the implicit function theorem reveal the following:
Proposition 1: L∗c , the amount of labor a household devotes to occupying land has the
following comparative statics:
dLc
dA=
αFL(TH , L − Lc)
αAtFLL(TH , L − Lc) + βg′(Lc)E[V (TH) − V (TL)]< 0 (8)
d2Lc
dAdα= βg′(Lc)E[V (TH) − V (TL)] < 0 (9)
d2Lc
dAdTL
= βg′(Lc)r > 0 (10)
That is, we expect land occupations to increase following a negative productivity shock,
and this effect is larger when the invaders are land poor, as well as areas with a larger
fraction of fixed rent contracts(high α).
An interesting lack of a clean comparative static is given by:
d2Lc
dAdTH
= αFLT (TH , L − Lc)(αAtFLL(TH , L − Lc)
+βg′(Lc)E[V (TH) − V (TL)] − (αFLLT (TH , L − Lc) + βg′(Lc)dE[V (TL)]
dTL
which can be negative or positive. This is because employers owning large landholdings
increases the returns to working as well as the returns to expropriating land. Note that if
we allowed the employers to have a different quantity of land than the occupation target,
these effects would be separate. Increases in the the size of the occupation target landhold-
ing would increase appropriative activities, while increases in the employers landholdings
would decrease them. Thus, an increase in land inequality could reduce the amount of
12
land occupations that resulted from a productivity shock if it raised the returns to working
more than the returns to occupation.
4 Data
4.1 Land Invasions
We employ municipal-level data on land invasions provided by Brazil’s Pastoral Land
Commission (Comissao Pastoral da Terra – CPT) and Dataluta (Banco de Dados da Luta
pela Terra). This dataset provides one of the largest samples on redistributive conflict in
the literature, covering 5,299 land invasions. The data consist of the number of distinct land
invasions per year in each Brazilian municipality between 1988 and 2004.8 Additionally,
our data include the number of families participating in each land invasion. The CPT,
a church-based NGO that has been active since 1976, collects these data from various
sources.9
There may be concerns with the coverage of the reports: for example, they may be
systematically biased towards underreporting conflict in remote areas. All of our results are
qualitatively similar when we restrict our sample to only municipalities that have reported
invasion activity. There may also be systematic measurement error due to journalistic bias
towards overreporting the size of a land invasion. For this reason, we focus on the number
of invasions, which is relatively less vulnerable to such bias than reported size of invasions.
8The CPT defines land occupations as “collective actions by landless families that, by entering ruralproperties, claim lands that do not fulfill the social function” [CPT 2004, p. 215, authors’ translation].
9The CPT compiles information on land invasions from a range of data sources, including local, nationaland international news articles; state and federal government reports; reports from various organizationssuch as churches, rural unions, political parties and NGOs; reports by regional CPT offices; and citizendepositions [CPT 2004, pp. 214-26]. When data sources conflict, reports from regional CPT offices are used.In 2004, the CPT collected land invasion data from 171 sources. Repeated invasions of the same propertyin a given year are only counted once.
13
However, for comparison we also provide results for the number of families involved in
land invasions. In addition, we examine a binary measure of whether conflict occurred in
a municipality-year, as this measure may be less prone to measurement error.
4.2 Agricultural Income
Our primary independent variable of interest is agricultural income, which is measured
by crop revenue. Data on crop production are from statistics on municipal agriculture
production (Producao Agrıcola Municipal) from Brazil’s national census bureau (Insti-
tuto Brasileiro de Geografia e Estatıstica – IBGE). For each muncipality-year, we take a
revenue-weighted sum of the log crop yields (tons per hectare) as a measure of log agricul-
tural income [Jayachandran 2006; Kruger 2007]. This calculation includes the eight most
important crops in Brazil, which are cotton, rice, sugar, beans, corn, soy, wheat and cof-
fee [Helfand and Resende 2001, p. 36].10 We assume that municipalities take crop prices
as given in domestic and international markets. Given the difficulties of ongoing data
collection in rural areas, crop data are subject to numerous sources of measurement er-
ror. Macroeconomic conditions, including periods of hyperinflation, may also contribute to
measurement error. Measurement error in our data may also be nonclassical, highlighting
the need for an instrument.
4.3 Rainfall
We use rainfall as a source of exogenous variation in agricultural income. Daily rain-
fall data from 2,605 weather stations across Brazil for the 1985-2005 period are from the
Brazilian National Water Agency (Agencia Nacional de Aguas – ANA). In order to derive a
municipal-level measure of rainfall, we match municipalities to the nearest weather station
10Helfand also includes oranges, which are missing from our data.
14
within 50 kilometers. Municipalities without a weather station within this matching radius
were excluded. All of our results are robust to changing the acceptable matching radius
to values between 20 and 100 kilometers, as well as to clustering standard errors by rain
station.
Raw rainfall totals would be inappropriate to use in this context given the wide
range of climatic variation in a country the size of Brazil. A 10-centimeter drop in annual
rainfall may be expected to have different economic effects in arid regions of the Northeast
than in the temperate South. In order to measure comparably the effect of rainfall on
agricultural productivity, we transform the rain data as follows. Monthly rain totals are first
standardized by station-month, then summed across the twelve months of the year. These
annual totals are then standardized by station-year. Standardizing by month accounts for
seasonal patterns and may more closely identify aberrant rainfall years [Mitchell 2003].
Standardization also makes rainfall measurements comparable across municipalities since
agricultural production is likely to be adapted to the average level and variance of rainfall
in each municipality.
The primary measure of rainfall levels is the absolute value of standardized rainfall
because the relationship between rainfall and income changes is nonmonotonic. As shown
below, both drought and flooding are negatively correlated with agricultural income. For-
mally, the primary measure is given by:
z =
∣
∣
∣
∣
xit − xi
si
∣
∣
∣
∣
(11)
where rain observations x for every rain measuring station i and year t pair are standardized
by the mean xi and standard deviation si of the rain data from each rain station’s 21-year
(1985-2005) time-series.11 For this rainfall measure, xit is the annual sum of standardized
11While our agricultural income and land invasions data are limited to a shorter panel, we use this 21-year
15
monthly rainfall, given by:
xit =12
∑
m=1
ximt − xim
sim
(12)
For robustness, we also examined additional measures of rainfall. A second rainfall
measure is squared rain deviation, given by:
z =
(
xit − xi
si
)2
(13)
As a third rainfall measure, we use the absolute value of standardized annual rainfall,
without first standardizing by month. This more coarse measure is given by Equation 11,
where xit is now the measured rainfall for each station-year.12
We also examined various alternative rainfall measures, including non-standardized
measures, higher-order polynomials, and dummies for various rain thresholds. These alter-
native measures of rainfall are not employed as instruments because they are not as highly
correlated with agricultural income.
4.4 Land Inequality and Land Tenure
Municipal-level data on the distribution of land in 1992 and 1998 were calculated from
INCRA’s land registry by Rodolfo Hoffmann [Hoffmann 1998]. In addition to Gini coeffi-
cients of the land distribution, these data contain the number of properties within given
size brackets in each municipality. Because the land Ginis were calculated based only on
landowners, we adjusted them using the share of population that is landless in each munic-
ipality, taken from the 1995/96 IBGE Agricultural Census. To reduce measurement error
and increase the sample size, we average the 1992 and 1998 observations where both are
rainfall data series for standardization in order to attain a better measure of the local rainfall conditions.12See appendix for additional details on the rain data, particularly on the handling of missing data.
16
available, and take the available observation from 1992 or 1998 otherwise. Endogeneity of
inequality to land invasions is not a concern given how persistent land inequality is over
time, with an intertemporal correlation of approximately 0.9 between Hoffmann’s 1992 and
1998 observations.
Because our dependent variable is a measure of redistributive conflict, we construct
a measure of economic polarization [Esteban and Ray 1994; Duclos, Esteban, and Ray
2004].13 This measure, while closely linked to the Gini coefficient, captures the degree of
bimodality in the distribution of land. Esteban and Ray [1999] argue that polarization is
a better predictor of conflict than the Gini coefficient.
Data on three types of land tenure—rental, ownership, and sharecropping—also
come from the 1995/96 IBGE Agricultural Census. Landholding is classified as rental if
the tenant pays the owner a fixed amount of money in rent, or if the tenant must meet a
production quota. Sharecropping, on the other hand, refers to properties in which tenants
pay owners a certain share (a half, quarter, etc.) of the harvest. When a landowner engages
in production, land is classified in the “ownership” category.14 We measure these variables
as the fraction of a municipality’s arable land under each land contract system.
13Polarization is calculated using discrete distribution data by the formula
�
i
�
j
π(1+α)i πj |µi − µj |
where π is the fraction of landowners in group i or j, and µ is the share of land owned by the correspondinglandowners, for all pairs of i and j [Esteban, Gradın, and Ray 2005]. In this study, we let α = 0.5.
14These three categories, as shares of arable land, do not sum to one because the Agricultural Censushas a fourth category of land, land that is “occupied,” or invaded. We exclude this category due to obviousendogeneity concerns with the dependent variable, not to mention the fact that it is probably more time-variant than the other three types of land tenure.
17
4.5 Other Variables
Data on rural population, poverty rates, income Gini coefficients and per capita income are
from the 1991 and 2000 national censuses.15 Data on agricultural workers and the quality
of land come from the 1995/96 Agricultural Census. IBGE administers both national
and agricultural censuses and also provides land area data. Annual population data and
municipal budget data are from the Institute for Applied Economic Research (Instituto de
Pesquisa Economica Aplicada – IPEA), a Brazilian government agency. Data on municipal
elections comes from the Supreme Electoral Court (Tribunal Superior Eleitoral – TSE). All
analysis is restricted to municipalities with more than 10 percent rural population (averaged
for the 1991 and 2000 census years), though results are robust to different thresholds.
Table 1 lists summary statistics for the variables included in the fixed-effects spec-
ifications. The top half of the table describes data used in the 14-year panel with annual
crop data, and the bottom half describe census data we use as a robustness check. We
add 0.01 before calculating log families, resulting in a negative mean for the variable. The
political competition variable is defined as the difference in vote share received by the top
two mayoral candidates in the last mayoral election (mayors were elected in 1996, 2000,
and 2004).16
5 Identification Strategy
Endogeneity is an important issue when estimating the relationship between economic
conditions and conflict. In our study, there may be reverse causation because land inva-
sions may reduce agricultural income by preventing harvesting. Another potential source
15Our primary measure of agricultural income is discussed above (Section 4.2). Census data on per capitaincome are used as a robustness check in Section 6.
16Mayors were also elected in 1988 and 1992, but electoral data are incomplete for this period, so wecannot compute the degree of political competition. We thank David Samuels for sharing with us the partialdata he compiled for this earlier period.
18
of bias is that agricultural income may be correlated with omitted variables that covary
with land invasions. Although we use municipality and year fixed effects, there may also
be municipality-specific, time-varying omitted variables such as the number of activists in
the area or the responsiveness of local judges to landowners’ complaints. One important
potential confounder is differential trends across municipalities, such as urbanization and
the expansion of education, that are correlated with income growth, but that also facili-
tate collective action [Putnam, Leonardi, and Nanetti 1994; Miguel, Gertler, and Levine
2006]. This phenomenon would bias OLS estimates towards 0: while rising income would
diminish the incentive to invade land, rising organizational capacity, for example, would
simultaneously make it less costly. The measurement error concerns discussed above may
also bias our estimates, and may be exacerbated by the inclusion of fixed effects.
Our identification strategy uses rainfall as an instrument for rural income. Rainfall
is a particularly good instrument for this study because land invasions occur in rural
municipalities, which are sensitive to weather variation. Below, we show that rainfall
is strongly correlated with municipal-level agricultural income, and then discuss possible
violations of the exclusion restriction. Our first-stage equation models the relationship
between rainfall and agricultural income:
yit = D1Zit + D2Xit + δi + δt + µit (14)
In this equation, rainfall deviations (Zit) instrument for agricultural income (yit) in mu-
nicipality i in year t. We control for other municipality characteristics (Xit). Municipality
fixed effects (δi) are included in all specifications to control for omitted, time-invariant
characteristics of municipalities that may be related to both agricultural income and land
invasions, such as total land area and soil quality. We also include year fixed effects (δt) in
all specifications to control for time-varying, national-level trends, as discussed in Section
19
2. The term µit is an error term, clustered at the municipal level. Clustering on rain sta-
tion and micro-region yield qualitatively similar results.17 Results are broadly comparable,
though weaker, when using lagged rainfall as an instrument for agricultural income.
The first-stage relationship between rainfall deviation and agricultural income is
strongly negative and significant at over 99 percent confidence (Table 2). This result is
robust to all three transformations of rainfall discussed in Section 4.3. The strength of
the first-stage relationship using all three measures is remarkable, with F -statistics for the
excluded instruments around 90 for the absolute value measures (Columns 1 and 3) and
about 75 for the squared rainfall (Column 2). By contrast, cross-country studies that use
rainfall as an instrument for GDP [e.g., Miguel, Satyanath, and Sergenti 2004] have suffered
from weak instrument problems [Bound, Jaeger, and Baker 1995; Staiger and Stock 1997].
Possible reasons for this difference may include our use of agricultural income instead of
GDP and our much greater sample size.
As a falsification exercise, we regress agricultural income on future rainfall, control-
ling for time and municipality fixed effects. Column 4 presents a specification that includes
rainfall at time t + 1 as well as at t. Future rainfall does not predict present agricultural
income: the coefficient on future rainfall is very small and statistically insignificant.
To justify our choice of using the absolute value of the standardized rainfall measure,
Figure 3 shows a nonparametric graph of agricultural income on the standardized rainfall
measure. This strong relationship is clearly nonmonotonic, approximately exhibiting an
inverted-U shape. Figure 4 displays the first-stage relationship using the absolute value
of rainfall deviation, which is clearly downward sloping. Interestingly, both droughts and
floods in Brazil are associated with lower agricultural income, a result that contrasts with
findings from some other contexts, including Africa [Miguel, Satyanath, and Sergenti 2004]
17As discussed below, micro-regions are defined by IBGE as contiguous municipalities in a given statethat share an urban center and have similar demographic, economic, and agricultural characteristics.
20
and India [Besley and Burgess 2002], which find that floods increase crop yields.
The second-stage equation estimates the impact of agricultural income on different
measures of land conflict (Cit):
Cit = β1yit + β2Xit + δi + δt + εit (15)
With respect to the exclusion restriction, a potential problem could be that rainfall
directly affects the decision to invade land. By using rain deviations as our instrument,
we mitigate this concern. One would have to believe that both droughts and floods have
an impact on the decision to invade land, which we find implausible. Even if this were the
case, our estimates would in fact be biased towards zero.
6 Basic Results
Negative income shocks, instrumented by rainfall, cause an increase in land invasions across
all three of our dependent variables. Table 3 presents linear probability model specifica-
tions, in which the dependent variable is a dichotomous indicator of whether or not a land
invasion occurred. Municipality and year fixed effects are included in all specifications but
are not shown.
The OLS estimate of the effect of agricultural income on land invasions is not sta-
tistically significant, possibly due to the biases discussed above (Section 5). Columns 2
through 4 present coefficient estimates and t-statistics for the IV-2SLS specifications using
each of our rain measures. Results are stable across all three instruments: all are statis-
tically significant at 99 percent confidence. A one standard deviation drop in agricultural
income increases the probability of a land invasion by 15 percentage points when instru-
menting with the absolute monthly standardized rainfall measure (Column 2). The effect
21
is 17 percentage points for the yearly standardized measure (Column 4), and nearly 22
percentage points when using squared standardized rainfall (Column 3). As a benchmark,
Miguel, Satyanath, and Sergenti [2004, p. 740] find that a standard deviation income shock
increases the probability of civil war by 12 percentage points. In our results, the effect of
an agricultural income shock ranges from nearly 4 to 5.5 times greater than the average
probability of a land invasion (4 percent).
Reduced form estimates of the direct effect of rainfall on land invasions are positive
and significant at 99 percent confidence (Columns 5-7). Deviations from average rainfall
are associated with a higher probability of land invasions. The estimated effects in the
reduced form, however, are quite small. A standard deviation increase in the rainfall
measure is associated with a 0.2 to 0.35 percentage point increase in the probability of a
land invasion.
Table 4 presents OLS reduced form specifications of the effect of three rainfall
measures on a count measure of land invasions (Columns 1-3), as well as on the log of
the number of families participating in land invasions (Columns 4-6). Rainfall coefficient
estimates are significant at 99 percent confidence or greater for all specifications. Once
again, the magnitudes of the coefficients are small.
Fixed-effects instrumental-variables estimates with the number of land invasions
and log families as dependent variables are shown in Table 5. Results are consistent with
the linear probability model. OLS estimates of agricultural income on both dependent vari-
ables are small and statistically insignificant (Columns 1 and 5). In the 2SLS estimates,
however, the coefficients are negative and significant at 99 percent significance on both de-
pendent variables. A standard deviation drop in agricultural income increases the number
of land invasions by between 0.31 and 0.46, depending on the choice of rainfall instrument
(Columns 2-4). In Columns 6-8, a 10 percent decrease in agricultural income causes a 9.7
22
to 14 percent increase in the number of families participating in land invasions.
We run several robustness checks to test our research design and data quality. First
is the test using future rainfall, described above. Second, we use a different measure of
income, from the 1991 and 2000 IBGE census. Specifications using only these two years,
shown in Table 6, provide an alternative measure of income. In Column 1, the OLS
estimate of the relationship between income and land invasions is negative and statistically
significant. Column 2 shows that census income is positively and significantly correlated
with our rainfall instrument. Column 3 shows that the IV-2SLS estimate of land invasions
on census income is negative and significant.
Third, we test the effect of rural unemployment on land invasions, another channel
by which economic shocks may affect redistributive conflict. Specifications using unem-
ployment are shown in Columns 4-6 of Table 6. As expected, Column 4 finds a positive
coefficient on census unemployment, statistically significant at 95 percent confidence. How-
ever, as shown in Column 5, rainfall is weakly correlated with unemployment and is thus
an inadequate instrument for unemployment. Hence, the IV-2SLS estimate in Column 6 of
the effect of rural unemployment on land invasions is not statistically significant. Column
7 reports the OLS reduced-form regression of rainfall on land invasions in the two census
years, further confirming our baseline results in this much smaller sample.
Fourth, another potential source of bias is a selection effect in the reporting of
land invasions, i.e. remote municipalities may be underreported. To check for this bias, we
restrict the sample to the 994 municipalities with at least one land invasion in the 1988-2004
period. IV-2SLS estimates of the effect of agricultural income on land invasions, shown in
Table 7, are significant at 99 percent confidence. Coefficient estimates are over three times
larger in magnitude than those estimated using the full sample. These findings suggest
that our results are not driven by selectivity in land invasion reporting. Furthermore,
23
agricultural income shocks affect the intensity of rural conflict, not just the outbreak of
conflict.
7 Exploring Heterogeneity
In this section, we examine whether the effect of income shocks on land invasions varies
across municipalities with different levels of land inequality and other characteristics.
7.1 Land Inequality
The effect of income shocks on land invasions is heterogeneous by land inequality. Table
8 displays estimated coefficients for specifications of interactions between land inequality
(Gi) and agricultural income (yit). More specifically, we instrument income (yit) with
rainfall (Zit, as described above), and instrument the interaction of land inequality and
income (Gi × yit) with the interaction of land inequality and rainfall (Gi × Zit). In Col-
umn 1, the coefficient on (Gi × yit) is negative and significant, while the coefficient on
agricultural income (yit) is now positive and significant. The effect of income at the mean
level of land inequality is still negative (-0.272) and similar to our previous estimates. In
municipalities with high inequality, negative income shocks have a greater positive effect
on land invasions. The estimates on the interaction imply that at the 90th percentile of the
land Gini distribution, a one standard deviation fall in agricultural income increases land
occupations by 0.76. This is twice as large as the effect at the mean level of inequality,
where a standard deviation drop in income causes 0.37 more invasions.
When applying these estimates to the high variation in state-level land inequality
across Brazil, substantially different effects of income shocks are predicted. In highly
unequal states, such as Amazonas (land Gini = 0.93) and Para (land Gini = 0.86), a one
standard deviation fall in income causes 0.85 and 0.72 more land invasions, respectively.
24
By contrast, in states with much lower levels of land inequality, such as Santa Catarina
(land Gini = 0.60) and Sao Paulo (land Gini = 0.64), a one standard deviation fall in
income causes only 0.02 and 0.12 more land invasions, respectively.
We also examine a measure of polarization, developed by Esteban and Ray [1994]
and Duclos, Esteban, and Ray [2004], interacted with agricultural income (Column 2).
The coefficient on this interaction is negative, significant, and larger in magnitude than
the corresponding coefficient in Column 1. At the 90th percentile of the polarization
distribution, a standard deviation drop in income increases land invasions by 1.11. Column
3 shows the “horse-race” regression of the two inequality interactions and finds that the
land-Gini interaction is statistically insignificant when the land polarization interaction is
included. This finding supports the theoretical predictions of Esteban and Ray [1999], who
argue that polarization better predicts conflict than the Gini coefficient.
Next, we disaggregate the land distribution. Column 4 shows the share of land
owned by the top 10 percent and bottom 50 percent of landowners, as well as the fraction
of the population that is landless. Only the interaction between the fraction of landless
and agricultural income is significant, which may suggest that the landless are the most
likely to invade land in response to a negative income shock.
Column 5 interacts the agricultural income shock with a dummy indicating whether
income is increasing or decreasing, finding that both are significant and nearly identical in
magnitude. This estimate suggests no heterogeneity in the effects of positive and negative
economic shocks. Column 6 shows that in low land-inequality (i.e. below median) munic-
ipalities, both positive and negative shocks have small yet insignificant effects. Column 7
reports the same specification as Columns 5 and 6, restricted to high land-inequality (i.e.
above median) municipalities. While the significance drops to the 90 percent confidence
level, the magnitudes of the coefficients are about three times the corresponding coeffi-
25
cients in the full-sample specification. Overall, these results show that land inequality is a
substantial source of heterogeneity in the effect of income shocks on land invasions.
Figure 5 graphically depicts this heterogenous effect of income by land inequality.
The two plots are the nonparametric reduced-form regressions of land invasions on rain-
fall, one restricted to high land-inequality municipalities and the other to low inequality
municipalities, as in Columns 6 and 7 of Table 8. While the standard error bands are
wide in places, the figure suggests that the effect of rainfall on land invasions is much
greater in municipalities with higher land inequality. This nonparametric result is consis-
tent with the estimates from the instrumental-variables specifications with land-inequality
interactions.
7.2 Land Tenure
In addition to land inequality, different systems of land tenure also mediate the effect of
income shocks on land invasions. We investigate three systems of land contracts—rental,
ownership, and sharecropping. In the theory of agrarian contracting under uncertainty, it
is well known that fixed-rent contracts entail tenants bearing the full effect of productivity
shocks [Otsuka and Hayami 1988; Stiglitz 1974]. Thus, we would expect that in municipal-
ities with a large share of renters, income shocks would cause more invasion activity.
Table 9 shows model specifications that include interactions with land tenure vari-
ables in addition to the interaction between land inequality and agricultural income.18
The bottom row of the table shows the effect of income with the interacted variables set
to their mean values. The mean effect of income is stable across specifications. Columns
1 through 3 display coefficient estimates for the interactions of the three land contract
18Substituting the land polarization measure for the land Gini in the interactions shown in Table 9yields broadly similar results on the land tenure variables. Results are also consistent when the land Giniinteraction is excluded.
26
variables, measured as a fraction of arable land, with agricultural income, each entered
separately. Column 4 includes all three interactions together, and Columns 5 through 7
replicate Columns 1 through 3 but with the addition of a triple interaction of land tenure,
land Gini, and income.
The sign on the land rental interaction in Column 1 is negative and statistically
significant with 99 percent confidence, indicating that income shocks cause more land
invasions in municipalities with a relatively greater share of land under rental contracts.
This effect is robust to the inclusion of the other tenure variables, as shown in Column 4,
and to the addition of a triple interaction (Column 5), though significance drops to the 90
percent confidence level.19 The triple interaction indicates that municipalities with high
land inequality and a high percentage of land under fixed-rent contracts experience more
land invasions with a decrease in income.
The land ownership interaction (Column 2), on the other hand, is positive, sug-
gesting that the effect of income shocks on land invasions is lower in municipalities where
more land is worked by its owners. This effect, however, is not robust to the inclusion of
the other tenure variables, nor to the addition of a triple interaction of landownership, land
Gini, and income, as shown in Column 6. The sharecropping interaction is not significant
in any specification.
There are several explanations for these results, but our aggregate data do not
enable us to distinguish among them. It may be that fixed-rent tenants have a greater
knowledge of farming, and thus stand to gain the most from invading land. It may also
be that land renters are more exposed to risk than other tenants, as suggested above, be-
cause they bear the full productivity shock and cannot use their land for collateral—unlike
19The distribution of the tenure variables are clustered around 0 (renting and sharecropping) and 1(ownership), with long, narrow tails. One could be concerned that these results are driven by outliers.However, excluding the extreme 1 percent of outlying observations yields nearly identical results, suggestingthat the outliers are not driving this result.
27
landowners—to borrow during poor seasons. This explanation would also account for the
positive coefficient on the interaction between income and the prevalence of owner-operated
farms.20 Hence, these results suggest that not only the concentration of landownership but
also the systems of land tenure employed affect the degree to which income shocks lead to
redistributive conflict.
These results should be interpreted with caution, however, because land tenure may
be endogenously time-varying. Land contracts could be renegotiated following a productiv-
ity shock, leading the choice of land contract to be correlated with income. Unfortunately,
we do not have multiple observations of land tenure systems within the sample period.
Nevertheless, other data suggest that land tenure systems are relatively stable over time
in Brazil. The fraction of land under rental contracts in the 1995/96 Agricultural Census
is highly correlated with the 1985 Agricultural Census observation (r = 0.60); intertempo-
ral correlations on the other tenure variables are comparable. Our results are suggestive,
however, and future research should consider the relationship between land contract choice
and conflict.
7.3 Other Interactions
We also inspect whether other mechanisms mediate the effect of income shocks on land
invasions. Coefficient estimates for specifications with other interactions are shown in
Table 10. Overall, we find no further evidence of heterogeneity. Column 1 interacts the
number of rural banks and agricultural income; the coefficient is small and insignificant.
Second, we examine municipal expenditures on public security, which may increase the
costs of invading land and thus dampen the effect of income shocks on land invasions.
20Recall also that any landless wage workers hired by these owner-operators are factored into the landGini, the interaction of which remains negative in these specifications.
28
The coefficient is small and insignificant (Column 2).21 Third, we consider public social
expenditures, which may increase or decrease the effect of income shocks on land invasions.
While social programs may offer a substitute to land occupations, they may also serve a
complementary role. If the poor use social programs as a substitute for invading land
when faced with income shocks, then higher public social expenditures may reduce land
invasions. But if invaders can draw on social programs while occupying land, then higher
government social expenditure may reduce the cost of land invasions and thereby increase
their frequency. Column 3 interacts municipal social expenditures with agricultural income
and finds a small and insignificant effect.
As the rest of the table shows, neither income inequality, the fraction of unused
arable land, nor political competition significantly affect the relationship between income
shocks and land conflict. We also interacted numerous other variables with agricultural
income including agricultural capital intensity (number of tractors), the presence of FM or
AM radio stations, and the political party of the mayor. None of these interactions were
significant (not reported).22 In sum, we find no evidence of heterogeneity across observables
other than land inequality and land tenure.
8 Land Inequality in the Cross-Section
We now explore the between-variation in land invasions. As above, three dependent vari-
ables are examined: the number of land invasions, a dummy indicating the presence of at
least one land invasion, and the number of families participating in land invasions. For this
section, each of these variables were aggregated for each municipality over the 1988-2004
21Note that most security spending is at the state level in Brazil. The Polıcia Militar is controlled at thestate level, and only some larger municipalities have significant police forces of their own. The interactionof state public security expenditures and agricultural income (not reported) is also insignificant.
22Furthermore, none of these interactions are significant even if the land Gini interaction is excluded.
29
period. For our independent variables, we take the earliest measurement available during
the sample period. Census data covariates are from 1991, while Agricultural Census data
are from 1995/96. Descriptive statistics for the cross-section are provided in Table 11. We
estimate OLS regressions using the following specification:
Ci = βXi + δji + εi (16)
where Xi denotes a vector of independent variables, δji denotes a micro-region j fixed effect,
and εi is an error term. Micro-regions are defined by IBGE as contiguous municipalities
in a given state that share an urban center and have similar demographic, economic, and
agricultural characteristics. All standard errors are clustered by micro-region. Coefficient
estimates and t-statistics are reported in Table 12.
Land inequality is positively associated with land invasions across all specifications
in Table 12. In Column 1, which does not include micro-region fixed effects or clustering,
land Gini and the land tenure variables, as well as numerous other independent variables,
are statistically significant. However, when we control for micro-region fixed effects (Col-
umn 2), only land inequality remains statistically significant. The coefficient magnitude
remains fairly stable, falling from 2.98 to 2.83 when including micro-region fixed effects
and clustering. Altogether, these estimates imply that a one standard deviation increase
in land inequality is associated with an increase of .37 to .39 land invasions. Given that the
mean number of land invasions across municipalities is 1.02, these coefficients represent a
large shift relative to the mean. We also fit a negative binomial model (Column 3), which
also yields highly significant results.23
Looking at the binary dependent variable, Column 4 shows that land inequality
23For situations in which the incidence of an event increases the probability that another event willoccur, as we assume to be the case for land invasions, negative binomial regression is more appropriate thanPoisson regression for event counts [Long 1997, p. 230-6].
30
remains the only statistically significant independent variable when micro-region fixed ef-
fects are included. Results are consistent when using log families as a dependent variable
(Column 5). These coefficients imply that a one standard deviation increase in land in-
equality is associated with 6.9 percent increase in the probability of a land invasion and
a 75 percent increase in the number of families participating in land invasions. The dif-
ference of these magnitudes suggests that the effect of land inequality on land invasions
operates substantially more on the intensive margin than the extensive margin. However,
these cross-municipality specifications may suffer from the omitted variables bias mentioned
above.
9 Conclusion
Our estimates show that adverse economic shocks, instrumented by rainfall, cause the
rural poor to occupy large landholdings. In highly unequal municipalities, negative income
shocks cause twice as many land invasions than in municipalities with average land in-
equality. We find even stronger effects using land polarization instead of the land Gini. In
addition, municipalities with relatively more land under rental contracts are more likely to
have a land invasion following a poor crop. There is no further evidence of heterogeneity by
other variables. Cross-sectional specifications support our claim on the importance of land
inequality in explaining land invasions. Our results are consistent with extensive qualitative
research on how economic conditions affect redistributive conflict in rural contexts.
This paper highlights an understudied cost of inequality: open, extralegal redistrib-
utive conflict. Land inequality may be associated with poor political institutions, thereby
channelling redistributive pressures into extralegal social-movement activity. Furthermore,
by creating incentives to engage in costly land invasions and by exposing a larger fraction
of the population to the risk of income shocks, land inequality may lead to a suboptimal
31
allocation of resources.
Our paper also follows a long tradition in the qualitative literature on the role of
economic institutions in agrarian redistributive conflict. Land contracts, by regulating the
distribution of risk between landlords and tenants, may influence the propensity of the
land-poor to engage in conflict during a negative productivity shock. Our results support
the claim that independent peasants are more likely to engage in open conflict to secure
land.
Empirical research on the economic determinants of conflict is relatively new. This
paper has contributed to this literature by examining the effect of economic conditions on
land invasions. Future research would ideally use individual-level panel data in order to
directly test if shocks to individual income cause participation in land invasions. Finally,
while this paper has largely looked at the demand-side determinants of land occupations,
a fascinating area of research is on the supply side. Identifying strong research designs for
examining the role of social movements and organization on redistributive conflict is an
important future task.
10 Appendix
On the Calculation of Rainfall Instruments
The daily rainfall data from the ANA contain some missing daily rainfall observations.
This could be due to, for example, a malfunctioning of the rain gauge. Many missing
days could potentially bias our rainfall measure, as we could miscalculate the degree to
which a given year deviated from average rainfall levels. To mitigate this concern, we
compute average daily rainfall—rather than total rainfall—and drop years that have too
many missing days.
32
What determines “too many” missing daily observations differs across our rain
measures. For the monthly standardized measure, only months with greater than 21 days
of valid rain observations were included, and years with fewer than 10 valid months were
similarly excluded. For the yearly standardized rain measure, only years with at least
335 valid days (i.e., 11 months, plus or minus) were included. Due to this difference,
the yearly measure has fewer valid station-year observations, because the monthly measure
permits more missing daily rain observations—provided that the missing days are scattered
throughout the year, not clustered in one or two months.
References
Acemoglu, D., and J. Robinson (2001): “A Theory of Political Transitions,” The
American Economic Review, 91(4), 938–963.
(2006): Economic Origins of Dictatorship and Democracy. Cambridge UP, New
York.
Alesina, A., and R. Perotti (1996): “Income distribution, political instability, and
investment,” European Economic Review, 40(6), 1203–1228.
Alesina, A., and D. Rodrik (1994): “Distributive Politics and Economic Growth,”
Quarterly Journal of Economics, 109(2), 465–90.
Alston, L., G. Libecap, and B. Mueller (1999): Titles, Conflict, and Land Use: The
Development of Property Rights and Land Reform on the Brazilian Amazon Frontier.
University of Michigan Press, Ann Arbor, MI.
Besley, T., and R. Burgess (2002): “The Political Economy of Government Respon-
siveness: Theory and Evidence from India,” Quarterly Journal of Economics, 117(4),
1415–51.
Bethell, L. (1987): Colonial Brazil. Cambridge UP, Cambridge.
33
Bound, J., D. Jaeger, and R. Baker (1995): “Problems with Instrumental Variables
Estimation When the Correlation between the Instruments and the Endogenous Ex-
planatory Variable Is Weak.,” Journal of the American Statistical Association, 90(430).
Cardoso, F. H. (1997): “Agrarian Reform in Brazil,” Discussion paper, Brasilia, Presi-
dent of the Republic.
Comparato, B. (2003): A Acao Polıtica do MST. Expressao Popular, Sao Paulo.
CPT (1988-2004): Conflitos no Campo. Comissao Pastoral da Terra, Goiania.
Do, Q.-T., and L. Iyer (2006): “An Empirical Analysis of Civil Conflict in Nepal,”
Working Paper.
Duclos, J., J. Esteban, and D. Ray (2004): “Polarization: Concepts, Measurement,
Estimation,” Econometrica, 72(6), 1737–1772.
Economist (2001): “Back to the Soil,” Economist, April 26.
Engerman, S., and K. Sokoloff (2001): “The Evolution of Suffrage Institutions in the
New World,” NBER Working Paper.
Esteban, J., C. Gradın, and D. Ray (2005): “Extensions of a Measure of Polarization,
with an Application to the Income Distribution of Five OECD Countries,” Working
Paper.
Esteban, J., and D. Ray (1994): “On the Measurement of Polarization,” Econometrica,
62(4), 819–851.
(1999): “Conflict and Distribution,” Journal of Economic Theory, 87, 379–415.
(2002): “Collective Action and the Group Size Paradox,” American Political
Science Review, 95(3), 663–672.
FAO (2005): “FAO Statistical Yearbook (http://www.fao.org/es),” New York, United
Nations.
Griffin, K., A. R. Khan, and A. Ickowitz (2002): “Poverty and the Distribution of
34
Land,” Journal of Agrarian Change, 2(2), 279–330.
Grossman, H. (1994): “Production, Appropriation, and Land Reform,” The American
Economic Review, 84(3), 705–712.
Grossman, H., and M. Kim (1995): “Swords or Plowshares? A Theory of the Security
of Claims to Property,” The Journal of Political Economy, 103(6), 1275–1288.
Helfand, S., and G. C. d. Resende (2001): “The Impact of Sector-Specific and
Economy-Wide Policy Reforms on Agriculture: The Case of Brazil, 1980-98,” Work-
ing Paper.
Hoffmann, R. (1998): “A Estrutura Fundiaria no Brasil de Acordo com o Cadastro do
INCRA: 1967 a 1998,” Discussion paper, UNICAMP Working Paper.
Huntington, S. (1968): Political Order in Changing Societies. Yale University Press,
New Haven, CT.
INCRA (2005): “Data from Incra Website (http://www.incra.gov.br/),” .
Jayachandran, S. (2006): “Selling Labor Low: Wage Responses to Productivity Shocks
in Developing Countries,” Journal of Political Economy, 114(3).
Keefer, P., and S. Knack (2002): “Polarization, Politics and Property Rights: Links
Between Inequality and Growth,” Public Choice, 111(1), 127–154.
Kruger, D. (2007): “Coffee Production Effects on Child Labor and Schooling in Rural
Brazil,” Journal of Development Economics, 82, 448–63.
Long, J. S. (1997): Regression Models for Categorical and Limited Dependent Variables.
Sage Publishers, Thousand Oaks.
Luebbert, G. (1991): Liberalism, Fascism or Social Democracy: Social Classes and the
Political Origins of Regimes in Interwar Europe. Oxford University Press, New York.
Machado, A., C. Magri, and M. Masagcao (1986): Radios livres: a reforma agraria
no ar. Brasiliense.
35
Markoff, J. (1996): The Abolition Of Feudalism: Peasants, Lords, and Legislators in the
French Revolution. Penn State Press.
Medeiros, L. S. d. (2003): Reforma Agraria no Brasil. Editora Fundacao Perseu Abramo,
Sao Paulo.
Miguel, E., P. Gertler, and D. Levine (2006): “Does Industrialization Build or
Destroy Social Networks?,” Economic Development and Cultural Change, 54(2), 287–
318.
Miguel, E., S. Satyanath, and E. Sergenti (2004): “Economic Shocks and Civil
Conflict: An Instrumental Variables Approach,” Journal of Political Economy, 112,
725–753.
Mitchell, T. (2003): “Northeast Brazil Rainfall Anomaly Index, 1849-2002,” Dis-
cussion paper, Joint Institute for the Study of the Atmosphere and Ocean,
http://jisao.washington.edu/data sets/brazil/.
Moore, B. (1966): Social Origins of Dictatorship and Democracy: Lord and Peasant in
the Making of the Modern World. Beacon Press, Boston.
Morissawa, M. (2001): A Historia pela Luta e o MST. Editora Expressao Popular, Sao
Paulo.
Otsuka, K., and Y. Hayami (1988): “Theories of Share Tenancy: A Critical Survey,”
Economic Development and Cultural Change, 37(1), 31–68.
Paiero, D., and J. Damatto (1996): Foices e Sabres: A Historia de uma Ocupacao dos
Sem-Terra. Anna Blume, Sao Paulo.
Paige, J. M. (1975): Agrarian Revolution: Social Movements and Export Agriculture in
the Underdeveloped World. Free Press, New York.
Palmeira, M., and S. Leite (1998): “Debates Economicos, Processos Sociais, e Lutas
Polıticas,” in Polıtica e Reforma Agraria, ed. by L. F. C. Costa, and R. Santos. MAUAD,
36
Rio de Janeiro.
Persson, T., and G. Tabellini (1993): “Is Inequality Harmful for Growth?,” Working
Paper.
Popkin, S. (1976): “Corporatism and Colonialism: The Political Economy of Rural
Change in Vietnam,” Comparative Politics, 8(3), 431–464.
Putnam, R., R. Leonardi, and R. Nanetti (1994): Making Democracy Work. Prince-
ton UP, Princeton.
Scott, J. (1976): The Moral Economy of the Peasant: Rebellion and Subsistence in
Southeast Asia. Yale University Press.
Simmons, A. (2001): “South Africa Razes Squatters’ Settlement,” Los Angeles Times,
July 13, A1.
Skocpol, T. (1979): States and Social Revolutions. Cambridge University Press, Cam-
bridge.
Staiger, D., and J. Stock (1997): “Instrumental Variables Regression with Weak In-
struments,” Econometrica, 65(3), 557–586.
Stiglitz, J. (1974): “Incentives and Risk Sharing in Sharecropping,” The Review of
Economic Studies, 41(2), 219–255.
Stinchcombe, A. L. (1961): “Agricultural Enterprise and Rural Class Relations,” Amer-
ican Journal of Sociology, 67, 165–76.
Wolf, E. (1969): Peasant Wars of the Twentieth Century. Harper & Row New York.
Wolford, W. (2001): “Grassroots-Initiated Land Reform in Brazil: The Rural Land-
less Workers’ Movement,” in Access to Land, Rural Poverty, and Public Action, ed. by
A. De Janvry, G. Gordillo, J.-P. Platteau, and E. Sadoulet. Oxford University Press,
Oxford; New York.
(2004): “Of Land and Labor: Agrarian Reform on the Sugarcane Plantation of
37
11 Figures
Figure 1: Families Involved in Land Invasions, 1988-2004
Source: CPT, Conflitos no Campo, 2004
39
Figure 2: Map of Rural Conflict
Note: Municipalities that experienced at least one occupation between 1988 and 2004 are shaded. Non-shaded municipalities did not experience land invasions
40
Figure 3: The First Stage: Nonparametric Regression of Agricultural Income on Standard-ized Rainfall
Locally weighted (lowess) regression of agricultural income on monthly standardized rainfall, conditionalon municipal and year fixed effects. Dashed lines represent 95 percent confidence bands.
41
Figure 4: The First Stage: Nonparametric Regression of Agricultural Income on AbsoluteStandardized Rainfall
Locally weighted (lowess) regression of agricultural income on monthly absolute standardized rainfall, con-ditional on municipal and year fixed effects. Dashed lines represent 95 percent confidence bands.
42
Figure 5: Nonparametric Regression of Land Invasions on Absolute Standardized Rainfall(Reduced Form)
Locally weighted (lowess) regression of land invasions (dichotomous) on monthly absolute standardizedrainfall, conditional on municipal and year fixed effects. Dashed lines represent 95 percent confidencebands.
43
Table 1: Descriptive Statistics for the Fixed-Effects Specifications
Variable N Mean SD
1991-2004Land Invasions, Dichotomous 52939 0.04 0.20Land Invasions, Count 52939 0.066 0.41Log (Families) 52939 -4.23 1.86Rain Deviation (Monthly) 52939 0.75 0.55Rain Deviation (Squared) 52939 0.86 1.16Rain Deviation (Annual) 50521 0.74 0.56Agricultural Income 52939 0.78 1.37Log (Population) 52939 9.22 0.93Land Gini 49756 0.74 0.14Polarization 49766 0.59 0.12Top 10% Landowners’ Share 49466 0.53 0.14Bottom 50% Landowners’ Share 49766 0.11 0.06Landless Population (Proportion) 49768 0.30 0.21Land with Fixed-Rent Tenure (Proportion) 49768 0.047 0.067Land with Ownership Tenure (Proportion) 49768 0.89 0.096Land with Sharecropping Tenure (Proportion) 49768 0.021 0.036Income Gini (Mean, 1991 and 2000) 52939 0.54 0.045Political Competition 34248 0.12 0.11Unused Arable Land (Proportion) 49768 0.048 0.071Banks (Mean, 1991, 1996, and 2000) 52939 1.47 1.90Log (Security Budget) 43968 -0.014 6.51Log (Social Spending) 43968 11.29 3.84
1991 and 2000Land Invasions, Count 7655 0.056 0.39Log (Families) 7655 -4.3 1.68Log(GDP per capita) 7655 4.81 0.56Rural Unemployment 7654 0.049 0.053Rain Deviation (Monthly) 7655 0.75 0.58Log (Population) 7655 9.25 0.92Income Gini 7655 0.55 0.06Log (Rural Population) 7655 8.33 0.92Education HDI 7655 0.72 0.13
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Table 2: Rainfall and Income (First Stage); DV: Agricultural Income
Ordinary Least Squares(1) (2) (3) (4)
Rain Deviation (Monthly) -0.040 -0.039(9.55)*** (8.67)***
(Rain Deviation)2 -0.016(8.63)***
Rain Deviation (Yearly) -0.042(9.54)***
Rain Deviation (Monthly), t + 1 -0.005(1.18)
Log (Population) -0.137 -0.138 -0.144 -0.140(3.68)** (3.70)** (3.76)** (3.60)**
Observations 52939 52939 50521 48118# of Municipalities 4221 4221 4114 4221F -statistic 91.17 74.53 90.97 38.37
Note: All specifications include municipal and year fixed effects and have standard errors clustered at themunicipal level. Robust t-statistics in parentheses. F -statistic corresponds to the test of the null hypothesisthat the coefficient on the excluded instrument equals zero.** p < .01, *** p < .001
Table 3: Agricultural Income and Land Invasions (Linear Probability)
IV-2SLS Reduced FormOLS Monthly Squared Yearly Monthly Squared Yearly(1) (2) (3) (4) (5) (6) (7)
Agricultural Income 0.0004 -0.109 -0.157 -0.125(0.27) (2.85)** (3.33)** (3.33)**
Rain Deviation 0.004(Monthly) (2.97)**
(Rain Deviation)2 0.003(3.60)**
Rain Deviation 0.005(Yearly) (3.56)**
Log (Population) 0.011 -0.004 -0.011 -0.005 0.011 0.011 0.013(1.18) (0.33) (0.79) (0.37) (1.13) (1.12) (1.33)
Observations 52939 52939 52939 50521 52939 52939 50521# of Municipalities 4221 4221 4221 4114 4221 4221 4114
Note: All specifications include municipal and year fixed effects and have standard errors clustered at themunicipal level. Robust t-statistics in parentheses.** p < .01
45
Table 4: Rainfall and Land Invasions (Reduced Form)
DV: Land Invasions, count DV: Log(Families)(1) (2) (3) (4) (5) (6)
Rain Deviation (Monthly) 0.009 0.039(3.12)** (2.88)**
(Rain Deviation)2 0.006 0.024(3.86)** (3.54)**
Rain Deviation (Yearly) 0.012 0.050(4.02)*** (3.67)**
Log (Population) 0.006 0.006 0.011 0.135 0.134 0.152(0.37) (0.36) (0.67) (1.50) (1.49) (1.65)
Observations 52939 52939 50521 52939 52939 50521# of Municipalities 4221 4221 4114 4221 4221 4114
Note: All specifications include municipal and year fixed effects and have standard errors clustered at themunicipal level. Robust t-statistics in parentheses.** p < .01, *** p < .001
46
Table 5: Income and Land InvasionsDV: Land Invasions, count DV: Log(Families)
IV-2SLS IV-2SLSOLS Monthly Squared Yearly OLS Monthly Squared Yearly(1) (2) (3) (4) (5) (6) (7) (8)
Agricultural Income 0.003 -0.224 -0.338 -0.285 0.007 -0.971 -1.436 -1.167(1.15) (3.02)** (3.62)** (3.76)** (0.48) (2.79)** (3.34)** (3.41)**
Log (Population) 0.007 -0.027 -0.043 -0.031 0.140 -0.008 -0.073 -0.019(0.45) (1.22) (1.71) (1.30) (1.55) (0.07) (0.58) (0.16)
Observations 52939 52938 52938 50520 52939 52938 52938 50520# of Municipalities 4221 4220 4220 4113 4221 4220 4220 4113
Note: All specifications include municipal and year fixed effects and have standard errors clustered at the municipal level. Robust t-statistics in parentheses.** p < .01
47
Table 6: Income, Unemployment, and Land Invasions; DV: Land Invasions, count
Income Unemployment ReducedOLS 1st Stage IV OLS 1st Stage IV Form(1) (2) (3) (4) (5) (6) (7)
Log (GDP per capita) -0.159 -2.459(3.51)** (3.87)**
Rural Unemployment 0.340 34.139(2.25)* (1.30)
Rain Deviation -0.022 0.002 0.054(Monthly) (5.54)*** (1.33) (5.13)***
Observations 7655 7655 7655 7654 7654 7654 7655# of Municipalities 4225 4225 4225 4225 4225 4225 4225F -statistic 30.67 1.76
Note: All specifications include municipal and year fixed effects and have standard errors clustered at themunicipal level. Robust t-statistics in parentheses. F -statistic corresponds to the test of the null hypothesisthat the coefficient on the excluded instrument equals zero. Coefficients for other included controls (IncomeGini, Log (Rural Population), Log (Population), and Education HDI score) are omitted.* p < .05, ** p < .01, *** p < .001
Table 7: Rainfall, Income, and Land Occupations in Municipalities with Invasion Activity
First DV: Land Invasions DV: Log(Families)Stage OLS IV OLS IV(1) (2) (3) (4) (5)
Rain Deviation (Monthly) -0.053(5.95)***
Agricultural Income 0.009 -0.700 0.013 -3.375(0.82) (2.88)** (0.25) (2.91)**
Log (Population) -0.170 0.031 -0.094 0.455 -0.144(2.37)* (0.59) (1.06) (1.56) (0.32)
Observations 12852 12852 12852 12852 12852# of Municipalities 994 994 994 994 994F -statistic 35.38
Note: Sample limited to municipalities that experienced at least one land occupation between 1988 and2004. All specifications include municipal and year fixed effects and have standard errors clustered at themunicipal level. Robust t-statistics in parentheses. F -statistic corresponds to the test of the null hypothesisthat the coefficient on the excluded instrument equals zero.* p < .05, ** p < .01, *** p < .001
48
Table 8: Land Inequality Interactions; DV: Land Invasions, count
Below AboveFull Median Median
Interactions Sample Inequality Inequality(1) (2) (3) (4) (5) (6) (7)
Agricultural Income 1.063 1.524 1.480 0.690(4.22)*** (3.35)** (2.96)** (0.79)
Land Gini -1.809 2.509× Agricultural Income (4.10)*** (1.15)
Polarization -3.136 -6.252× Agricultural Income (3.38)** (1.72)+
Top 10% Landowners’ Share -0.927× Agricultural Income (0.85)
Bottom 50% Landowners’ Share -0.021× Agricultural Income (0.01)
Landless Population -1.969× Agricultural Income (2.75)**
Increasing Agricultural -0.346 -0.044 -0.953Income (2.76)** (0.53) (1.94)+
Decreasing Agricultural -0.381 -0.041 -1.066Income (2.75)** (0.47) (1.95)+
Log (Population) -0.001 0.013 0.015 -0.011 -0.047 -0.017 -0.129(0.05) (0.43) (0.46) (0.31) (1.61) (0.67) (1.35)
Observations 49755 49765 49755 49455 52938 24868 24887# of Municipalities 3804 3805 3804 3778 4220 1912 1892Mean Effect of Income -0.272 -0.334 -0.372 -0.391
Note: Instrumental-variables regression with municipal and year fixed effects and with standard errors clustered at the municipal level.Instrumental variables are rain deviation (monthly) and rain deviation interacted with the relevant measure of land inequality. Robustt-statistics in parentheses.+ p < .10, * p < .05, ** p < .01, *** p < .001
49
Table 9: Interactions: Land Contracts; DV: Land Invasions, count
IV-2SLS(1) (2) (3) (4) (5) (6) (7)
Agricultural Income 1.318 0.197 1.127 1.708 -0.055 6.327 0.919(4.17)*** (0.38) (3.87)** (2.83)** (0.11) (1.62) (0.06)
Land Gini -1.999 -1.938 -1.876 -1.893 -0.231 -10.201 -1.582× Agricultural Income (4.07)*** (4.13)*** (3.95)** (3.90)** (0.33) (1.69)+ (0.08)
Fixed-Rent Tenure -3.269 -3.898 23.563× Agricultural Income (2.64)** (2.80)** (1.87)+
Fixed-Rent Tenure × Land Gini -36.288× Agricultural Income (1.92)+
Ownership Tenure 1.065 -0.511 -5.920× Agricultural Income (1.70)+ (1.07) (1.38)
Ownership Tenure × Land Gini 9.368× Agricultural Income (1.43)
Sharecropping -0.981 1.158 9.420× Agricultural Income (0.54) (0.59) (0.01)
Sharecropping × Land Gini -17.931× Agricultural Income (0.01)
Log (Population) 0.002 0.004 -0.002 0.002 0.019 0.014 0.001(0.08) (0.14) (0.09) (0.06) (0.52) (0.51) (0.00)
Observations 49755 49755 49755 49755 49755 49755 49755# of Municipalities 3804 3804 3804 3804 3804 3804 3804Mean Effect of Income -0.307 -0.284 -0.279 -0.307 -0.380 -0.315 -0.331
Note: Instrumental-variables regression with municipal and year fixed effects and with standard errors clustered at the municipal level.Instrumental variables are rain deviation (monthly) and rain deviation interacted with the relevant variable. Robust t-statistics in paren-theses.+ p < .10, * p < .05, ** p < .01, *** p < .001
50
Table 10: Interactions: Alternative Opportunities and State Capacity; DV: Land Invasions,count
IV-2SLS(1) (2) (3) (4) (5) (6)
Agricultural Income 2.084 1.377 1.326 0.946 1.043 1.601(1.62) (2.73)** (2.88)** (1.49) (4.13)*** (2.68)**
Land Gini -2.663 -2.200 -2.060 -1.823 -1.840 -3.283× Agricultural Income (1.92)+ (2.59)** (3.07)** (4.01)*** (4.11)*** (3.22)**
Banks -0.498× Agricultural Income (0.98)
Log(Security Budget) -0.016× Agricultural Income (0.40)
Log(Security Budget) 0.015(0.39)
Log(Social Spending) -0.003× Agricultural Income (0.33)
Log(Social Spending) 0.001(0.23)
Income Gini 0.226× Agricultural Income (0.19)
Unused Arable Land 0.846× Agricultural Income (1.04)
Political Competition 3.377× Agricultural Income (1.02)
Political Competition -2.942(1.00)
Log (Population) 0.102 0.008 -0.008 -0.001 -0.003 -0.014(0.92) (0.16) (0.28) (0.02) (0.14) (0.12)
Observations 49755 41745 41745 49755 49755 31268# of Municipalities 3804 3798 3798 3804 3804 3778
Note: Instrumental-variables regression with municipal and year fixed effects and with standard errorsclustered at the municipal level. Instrumental variables are rain deviation (monthly) and rain deviationinteracted with the relevant variable. Robust t-statistics in parentheses.+ p < .10, * p < .05, ** p < .01, *** p < .001
51
Table 11: Descriptive Statistics for the Cross-Sectional Specifications
Variable N Mean SD
Land Invasions (Count), 1988-2004 4062 1.02 3.28Land Invasions (Dichotomous), 1988-2004 4062 0.25 0.43Log (Families), 1988-2004 4062 -2.12 4.42
Land Gini 4062 0.75 0.13Log (GDP per capita), 1991 4062 4.62 0.54Unused Arable Land (Proportion) 4062 0.051 0.073Income Gini, 1991 4062 0.53 0.055Extreme Poverty (Percent), 1991 4062 33.53 19.81Log (Population), 1991 4062 9.35 0.89Log (Rural Population), 1991 4062 8.49 0.90Log (Land Area) 4062 6.30 1.26Education HDI, 1991 4062 0.64 0.13
Table 12: Total Land Invasions by Municipality, 1988-2004
DV: Invasions, DV: LogDV: Land Invasions, count dichotomous (Families)
NegativeOLS OLS Binomial OLS OLS(1) (2) (3) (4) (5)
Land Gini 2.983 2.829 4.609 0.527 5.776(6.62)*** (4.04)*** (6.19)*** (5.73)*** (6.07)***
Fixed-Rent Tenure 4.774 0.728 -0.748 -0.030 0.527(4.34)*** (0.41) (0.66) (0.19) (0.31)
Ownership Tenure 1.728 0.016 0.073 0.096 1.201(2.56)* (0.02) (0.08) (0.99) (1.18)
Log(GDP per -2.382 -0.747 -0.387 -0.094 -0.789capita), 1991 (5.06)*** (1.23) (0.64) (1.10) (0.92)
Extreme Poverty, -0.073 -0.013 0.001 -0.001 -0.0131991 (5.82)*** (0.98) (0.04) (0.59) (0.60)
Unused Arable -0.055 0.715 -0.514 -0.038 0.010Land (0.07) (0.92) (0.56) (0.29) (0.01)
Micro-region Fixed- no yes yes yes yesEffects Included
Observations 4062 4062 4013 4062 4062R2 0.08 0.34 0.39 0.41
Note: Coefficients for micro-region fixed effects and controls (Income Gini, log(Population), log(RuralPopulation), log(Land Area), and Education HDI) omitted. Standard errors clustered at the micro-regionlevel in columns 2-5. Robust t-statistics in parentheses.* p < .05, ** p < .01, *** p < .001
52