lecture 4: optimal labor income taxation · federal us income tax us income tax assessed on annual...

78
Lecture 4: Optimal Labor Income Taxation Stefanie Stantcheva Fall 2017 1 78

Upload: others

Post on 01-Jan-2020

7 views

Category:

Documents


0 download

TRANSCRIPT

Page 1: Lecture 4: Optimal Labor Income Taxation · FEDERAL US INCOME TAX US income tax assessed on annual family income (not individual) [most other OECD countries have shifted to individual

Lecture 4: Optimal Labor Income TaxationStefanie Stantcheva

Fall 2017

1 78

Page 2: Lecture 4: Optimal Labor Income Taxation · FEDERAL US INCOME TAX US income tax assessed on annual family income (not individual) [most other OECD countries have shifted to individual

TAXATION AND REDISTRIBUTION

Key question: Should government reduce inequality using taxes andtransfers?1) Governments use taxes to raise revenue2) This revenue funds transfer programs:a) Universal Transfers: Public Education, Health Care Benefits (only 65+ inthe US), Retirement and Disability Benefits, Unemployment benefitsb) Means-tested Transfers: In-kind (Medicaid, public housing, foodstampsin the US) and cash benefitsModern governments raise large fraction of GDP in taxes (30-45%) andspend significant fraction of GDP on transfers

2 78

Page 3: Lecture 4: Optimal Labor Income Taxation · FEDERAL US INCOME TAX US income tax assessed on annual family income (not individual) [most other OECD countries have shifted to individual

FACTS ON US TAXES AND TRANSFERS

References: Comprehensive description in:http://www.taxpolicycenter.org/taxfacts/A) Taxes: (1) individual income tax (fed+state), (2) payroll taxes on earnings(fed, funds Social Security+Medicare), (3) corporate income tax (fed+state),(4) sales taxes (state)+excise taxes (state+fed), (5) property taxes (state)B) Means-tested Transfers: (1) refundable tax credits (fed), (2) in-kindtransfers (fed+state): Medicaid, public housing, nutrition (SNAP),education, (3) cash welfare: TANF for single parents (fed+state), SSI forold/disabled (fed)

3 78

Page 4: Lecture 4: Optimal Labor Income Taxation · FEDERAL US INCOME TAX US income tax assessed on annual family income (not individual) [most other OECD countries have shifted to individual

FEDERAL US INCOME TAX

US income tax assessed on annual family income (not individual) [mostother OECD countries have shifted to individual assessment]Sum all cash income sources from family members (both from labor andcapital income sources) = called Adjusted Gross Income (AGI)(adjustments = some deduction e.g., for business expenses, certainretirement contributions, etc.).Main exclusions: fringe benefits (health insurance, pension contributions),imputed rent of homeowners, unrealized capital gains

4 78

Page 5: Lecture 4: Optimal Labor Income Taxation · FEDERAL US INCOME TAX US income tax assessed on annual family income (not individual) [most other OECD countries have shifted to individual

FEDERAL US INCOME TAX

Taxable income = AGI - personal exemptions - deductionpersonal exemptions = $4K * # family members (in 2016)deduction is max of standard deduction or itemized deductionsStandard deduction is a fixed amount depending on family structure($12.6K for couple, $6.3K for single in 2016)Itemized deductions: (a) state and local taxes paid, (b) mortgage interestpayments, (c) charitable giving, various small other items[Itemized deductions, called tax expenditures ≈ 10% of AGI]

5 78

Page 6: Lecture 4: Optimal Labor Income Taxation · FEDERAL US INCOME TAX US income tax assessed on annual family income (not individual) [most other OECD countries have shifted to individual

FEDERAL US INCOME TAX: TAX BRACKETS

Tax T (z) is piecewise linear and continuous function of taxable income zwith constant marginal tax rates (MTR) T ′(z) by bracketsIn 2013-2016, 6 brackets with MTR 10%,15%,25%,28%,33%,35%, 39.6% (topbracket for z above $470K), indexed on price inflationLower preferential rates (up to a max of 20%) apply to dividends (since2003) and realized capital gains [in part to offset double taxation ofcorporate profits]Tax rates change frequently over time. Top MTRs have declined drasticallysince 1960s (as in many OECD countries)

6 78

Page 7: Lecture 4: Optimal Labor Income Taxation · FEDERAL US INCOME TAX US income tax assessed on annual family income (not individual) [most other OECD countries have shifted to individual

0 taxable income z

T(z) is

continuous in z

slope

39.6%

slope

15% slope

10%

T(z) Individual Income Tax

Page 8: Lecture 4: Optimal Labor Income Taxation · FEDERAL US INCOME TAX US income tax assessed on annual family income (not individual) [most other OECD countries have shifted to individual

0 taxable income z

39.6%

15%

10%

Marginal Income Tax

T′(z) is a

step function

T′(z)

Page 9: Lecture 4: Optimal Labor Income Taxation · FEDERAL US INCOME TAX US income tax assessed on annual family income (not individual) [most other OECD countries have shifted to individual

Source: IRS, Statistics of Income Division, Historical Table 23

Page 10: Lecture 4: Optimal Labor Income Taxation · FEDERAL US INCOME TAX US income tax assessed on annual family income (not individual) [most other OECD countries have shifted to individual

FEDERAL US INCOME TAX: TAX CREDITS

Tax credits: Additional reduction in taxes(1) Non refundable (cannot reduce taxes below zero): foreign tax credit,child care expenses, education credits, energy credits, and many others(2) Refundable (can reduce taxes below zero, i.e., be net transfers): EITC(earned income tax credit, up to $3.3K, $5.5K, $6.1K for working familieswith 1, 2, 3+ kids), Child Tax Credit ($1000 per kid, partly refundable)Refundable tax credits are now the largest means-tested cash transfer forlow income families

10 78

Page 11: Lecture 4: Optimal Labor Income Taxation · FEDERAL US INCOME TAX US income tax assessed on annual family income (not individual) [most other OECD countries have shifted to individual

EITC Amount as a Function of Earnings

Earnings ($)

0 5000 10000 15000 20000 25000 30000 35000 40000

Subsidy: 34%

Subsidy: 40%

Phase-out tax: 16%

Phase-out tax: 21%

Single, 2+ kidsMarried, 2+ kids

Single, 1 kidMarried, 1 kid

No kids

EIT

C A

mou

nt ($

)

010

0020

0030

0040

0050

00

Source: Federal Govt

Page 12: Lecture 4: Optimal Labor Income Taxation · FEDERAL US INCOME TAX US income tax assessed on annual family income (not individual) [most other OECD countries have shifted to individual
Page 13: Lecture 4: Optimal Labor Income Taxation · FEDERAL US INCOME TAX US income tax assessed on annual family income (not individual) [most other OECD countries have shifted to individual

FEDERAL US INCOME TAX: TAX FILING

Taxes on year t earnings are withheld on paychecks during year t(pay-as-you-earn)Income tax return filed in Feb-April 15, year t + 1 [filers use eithersoftware or tax preparers, huge private industry, most OECD countriesprovide pre-populated returns]Most tax filers get a tax refund as withholdings larger than taxes owed ingeneralPayers (employers, banks, etc.) send income information to govt (3rd partyreporting)3rd party reporting + withholding at source is key for successfulenforcement

13 78

Page 14: Lecture 4: Optimal Labor Income Taxation · FEDERAL US INCOME TAX US income tax assessed on annual family income (not individual) [most other OECD countries have shifted to individual

MAIN MEANS-TESTED TRANSFER PROGRAMS

1) Traditional transfers: managed by welfare agencies, paid on monthlybasis, high stigma and take-up costs ⇒ low take-up rates (often onlyaround 50%)Main programs: Medicaid (health insurance for low incomes), SNAP(former food stamps), public housing, TANF (welfare), SSI (aged+disabled)2) Refundable income tax credits: managed by tax administration, paid asan annual lumpsum in year t + 1, low stigma and take-up cost ⇒ hightake-up ratesMain programs: EITC and Child Tax Credit [large expansion since the1990s] for low income working families with children

14 78

Page 15: Lecture 4: Optimal Labor Income Taxation · FEDERAL US INCOME TAX US income tax assessed on annual family income (not individual) [most other OECD countries have shifted to individual

KEY CONCEPTS FOR TAXES/TRANSFERS

[Next slide:] budget (z , z −T (z)) which integrates taxes and transfers1) Transfer benefit with zero earnings −T (0) [sometimes called demograntor lumpsum grant]2) Marginal tax rate (or phasing-out rate) T ′(z): individual keeps1−T ′(z) for an additional $1 of earnings (intensive labor supply response)3) Participation tax rate τp = [T (z)−T (0)]/z : individual keeps fraction1− τp of earnings when moving from zero earnings to earnings z (extensivelabor supply response):

z −T (z) = −T (0) + z · (1− τp)

4) Break-even earnings point z∗: point at which T (z∗) = 0 15 78

Page 16: Lecture 4: Optimal Labor Income Taxation · FEDERAL US INCOME TAX US income tax assessed on annual family income (not individual) [most other OECD countries have shifted to individual

0 pre-tax income z

Budget Set

-T(0)

𝑐= z-T(z) after-tax

and transfer

income

slope=1-T′(z)

z∗

Page 17: Lecture 4: Optimal Labor Income Taxation · FEDERAL US INCOME TAX US income tax assessed on annual family income (not individual) [most other OECD countries have shifted to individual

0 pre-tax income z

-T(0)

𝑐= z-T(z)

(1 − 𝜏𝑝)z

𝜏𝑝=participation tax rate

z

Page 18: Lecture 4: Optimal Labor Income Taxation · FEDERAL US INCOME TAX US income tax assessed on annual family income (not individual) [most other OECD countries have shifted to individual

US Tax/Transfer System, single parent with 2 children, 2009

$0

$10,000

$20,000

$30,000

$40,000

$50,000

$0

$10,

000

$20,

000

$30,

000

$40,

000

$50,

000Gross Earnings (with employer payroll taxes)

Dis

posa

ble

arni

ngs

$0

$10,000

$20,000

$30,000

$40,000

$50,000

Welfare:TANF+SNAP

Tax credits:EITC+CTC

Earnings afterFed+SSA taxes

45 Degree Line

Source: Federal GovtSource: Computations made by Emmanuel Saez using tax and transfer system parameters

Page 19: Lecture 4: Optimal Labor Income Taxation · FEDERAL US INCOME TAX US income tax assessed on annual family income (not individual) [most other OECD countries have shifted to individual

Source: Piketty, Thomas, and Emmanuel Saez (2012)

Page 20: Lecture 4: Optimal Labor Income Taxation · FEDERAL US INCOME TAX US income tax assessed on annual family income (not individual) [most other OECD countries have shifted to individual

Profile of Current Means-tested Transfers

Traditional means-tested programs reduce incentives to work for lowincome workersRefundable tax credits have significantly increased incentive to work forlow income workersHowever, refundable tax credits cannot benefit those with zero earningsTrade-off: US chooses to reward work more than most European countries(such as France) but therefore provides smaller benefits to those with noearnings

20 78

Page 21: Lecture 4: Optimal Labor Income Taxation · FEDERAL US INCOME TAX US income tax assessed on annual family income (not individual) [most other OECD countries have shifted to individual

Optimal Taxation: Case with No Behavioral Responses

Utility u(c) strictly increasing and concaveSame for everybody where c is after tax income.Income z is fixed for each individual, c = z −T (z) where T (z) istax/transfer on z (tax if T (z) > 0, transfer if T (z) < 0)N individuals with fixed incomes z1 < ... < zN

Government maximizes Utilitarian objective:SWF =

N∑i=1

u(zi −T (zi ))

subject to budget constraint∑N

i=1 T (zi ) = 0 (taxes need to fund transfers)21 78

Page 22: Lecture 4: Optimal Labor Income Taxation · FEDERAL US INCOME TAX US income tax assessed on annual family income (not individual) [most other OECD countries have shifted to individual

Simpler Derivation with just 2 individuals

maxSWF = u(z1 −T (z1)) + u(z2 −T (z2)) s.t. T (z1) + T (z2) = 0Replace T (z1) = −T (z2) in SWF using budget constraint:SWF = u (z1 + T (z2)) + u(z2 −T (z2))First order condition (FOC) in T (z2):

0 =dSWF

dT (z2)= u′ (z1 + T (z2))− u′(z2 −T (z2)) = 0⇒

u′(z1 + T (z2)) = u′(z2 −T (z2))⇒ u′(z1 −T (z1)) = u′(z2 −T (z2))

⇒ z1 −T (z1) = z2 −T (z2) constant across the 2 individualsPerfect equalization of after-tax income = 100% tax rate and redistribution.Utilitarianism with decreasing marginal utility leads to perfect egalitarianism[Edgeworth, 1897] 22 78

Page 23: Lecture 4: Optimal Labor Income Taxation · FEDERAL US INCOME TAX US income tax assessed on annual family income (not individual) [most other OECD countries have shifted to individual

Derivation with N individuals

Replace T (z1) = −∑N

i=2 T (zi ) from budget constraint:SWF = u

(z1 +

N∑i=2

T (zi )

)+

N∑i=2

u(zi −T (zi ))

First order condition (FOC) in T (zj ) for a given j = 2, ..,N :0 =

∂SWF

∂T (zj )= u′

(z1 +

N∑i=2

T (zi )

)− u′(zj −T (zj )) = 0⇒

u′(zj −T (zj )) = u′(z1 −T (z1))⇒ zj −T (zj ) = constant across j = 1, ..,NPerfect equalization of after-tax income = 100% tax rate and redistribution.

23 78

Page 24: Lecture 4: Optimal Labor Income Taxation · FEDERAL US INCOME TAX US income tax assessed on annual family income (not individual) [most other OECD countries have shifted to individual

0

Utilitarianism and Redistribution utility

consumption 𝑐 𝑐1 𝑐2 𝑐1 + 𝑐2

2

𝑢𝑐1 + 𝑐2

2

𝑢(𝑐1) + 𝑢(𝑐2)

2

Page 25: Lecture 4: Optimal Labor Income Taxation · FEDERAL US INCOME TAX US income tax assessed on annual family income (not individual) [most other OECD countries have shifted to individual

ISSUES WITH SIMPLE MODEL

1) No behavioral responses: Obvious missing piece: 100% redistributionwould destroy incentives to work and thus the assumption that z isexogenous is unrealistic⇒ Optimal income tax theory incorporates behavioral responses2) Issue with Utilitarianism: Even absent behavioral responses, manypeople would object to 100% redistribution [perceived as confiscatory]⇒ Citizens’ views on fairness impose bounds on redistribution govt can do[political economy / public choice theory]

25 78

Page 26: Lecture 4: Optimal Labor Income Taxation · FEDERAL US INCOME TAX US income tax assessed on annual family income (not individual) [most other OECD countries have shifted to individual

EQUITY-EFFICIENCY TRADE-OFF

Taxes can be used to raise revenue for transfer programs which can reduceinequality in disposable income ⇒ Desirable if society feels that inequalityis too largeTaxes (and transfers) reduce incentives to work ⇒ High tax rates createeconomic inefficiency if individual respond to taxesSize of behavioral response limits the ability of government to redistributewith taxes/transfers⇒ Generates an equity-efficiency trade-offEmpirical tax literature estimates the size of behavioral responses totaxation

26 78

Page 27: Lecture 4: Optimal Labor Income Taxation · FEDERAL US INCOME TAX US income tax assessed on annual family income (not individual) [most other OECD countries have shifted to individual

Labor Supply Theory

Individual has utility over labor supply l and consumption c : u(c , l)increasing in c and decreasing in l [= increasing in leisure]

maxc ,l u(c , l) subject to c = w · l + R

with w = w · (1− τ) the net-of-tax wage (w is before tax wage rate and τis tax rate), and R non-labor incomeFOC w ∂u

∂c +∂u∂l = 0 defines Marshallian labor supply l = l(w ,R)

Uncompensated labor supply elasticity: εu =w

l· ∂l∂w

Income effects: η = w∂l∂R ≤ 0

27 78

Page 28: Lecture 4: Optimal Labor Income Taxation · FEDERAL US INCOME TAX US income tax assessed on annual family income (not individual) [most other OECD countries have shifted to individual

0 l = labor supply

R Slope=wMarshallian Labor Supply l(w,R)

Indifference Curves

Labor Supply Theory

Budget: c = wl+R

c=z-T(z) consumption

Page 29: Lecture 4: Optimal Labor Income Taxation · FEDERAL US INCOME TAX US income tax assessed on annual family income (not individual) [most other OECD countries have shifted to individual

0 labor supply l

Labor Supply Income Effect

R l(w,R)

Budget: c = wl+R

c=z-T(z) consumption

Page 30: Lecture 4: Optimal Labor Income Taxation · FEDERAL US INCOME TAX US income tax assessed on annual family income (not individual) [most other OECD countries have shifted to individual

0 labor supply l

Labor Supply Income Effect

R l(w,R)

Budget: c = wl+R

Budget: c = wl+R+dR

c=z-T(z) consumption

R+dR

Page 31: Lecture 4: Optimal Labor Income Taxation · FEDERAL US INCOME TAX US income tax assessed on annual family income (not individual) [most other OECD countries have shifted to individual

0 labor supply l

Labor Supply Income Effect

R l(w,R) l(w,R+dR)

Budget: c = wl+R

Budget: c = wl+R+dR

η= w( l/ R) < 0 ∂∂

c=z-T(z) consumption

R+dR

Page 32: Lecture 4: Optimal Labor Income Taxation · FEDERAL US INCOME TAX US income tax assessed on annual family income (not individual) [most other OECD countries have shifted to individual

Labor Supply Theory

Substitution effects: Hicksian labor supply: lc(w , u) minimizes costneeded to reach u given slope w ⇒

Compensated elasticity εc = w

l· ∂l

c

∂w > 0

Slutsky equation ∂l∂w =

∂lc∂w + l

∂l∂R ⇒ εu = εc + η

Tax rate τ discourages work through substitution effects (work pays less atthe margin)Tax rate τ encourages work through income effects (taxes make you poorerand hence in more need of income)Net effect ambiguous (captured by sign of εu) 32 78

Page 33: Lecture 4: Optimal Labor Income Taxation · FEDERAL US INCOME TAX US income tax assessed on annual family income (not individual) [most other OECD countries have shifted to individual

0 labor supply l

Slope=w

Minimize cost to reach utility u given slope w: Hicksian Labor Supply lc(w,u)

Labor Supply Theory

utility 𝑢 c=z-T(z) consumption

Page 34: Lecture 4: Optimal Labor Income Taxation · FEDERAL US INCOME TAX US income tax assessed on annual family income (not individual) [most other OECD countries have shifted to individual

0 Labor supply l

Labor Supply Substitution Effect

Slope=w

utility 𝑢

lc(w,u)

c=z-T(z) consumption

Page 35: Lecture 4: Optimal Labor Income Taxation · FEDERAL US INCOME TAX US income tax assessed on annual family income (not individual) [most other OECD countries have shifted to individual

0 Labor supply l

Labor Supply Substitution Effect

Slope=w

utility 𝑢

slope= w+dw

εc= (w/lc) lc/ w>0

lc(w,u) lc(w+dw,u)

∂ ∂

c=z-T(z) consumption

Page 36: Lecture 4: Optimal Labor Income Taxation · FEDERAL US INCOME TAX US income tax assessed on annual family income (not individual) [most other OECD countries have shifted to individual

0 Labor supply l

Uncompensated Labor Supply Effect

slope=w

R Budget: c = wl+R

l(w,R)

c=z-T(z) consumption

Page 37: Lecture 4: Optimal Labor Income Taxation · FEDERAL US INCOME TAX US income tax assessed on annual family income (not individual) [most other OECD countries have shifted to individual

0 Labor supply l

Uncompensated Labor Supply Effect

slope=w

slope=w+dw

R

εu

l(w,R) l(w+dw,R)

c=z-T(z) consumption

Page 38: Lecture 4: Optimal Labor Income Taxation · FEDERAL US INCOME TAX US income tax assessed on annual family income (not individual) [most other OECD countries have shifted to individual

0 Labor supply l

Uncompensated Labor Supply Effect

slope=w

slope=w+dw

substitution effect: εc>0 R

εu

l(w,R) l(w+dw,R)

c=z-T(z) consumption

Page 39: Lecture 4: Optimal Labor Income Taxation · FEDERAL US INCOME TAX US income tax assessed on annual family income (not individual) [most other OECD countries have shifted to individual

0 Labor supply l

Uncompensated Labor Supply Effect

slope=w

slope=w+dw

substitution effect: εc>0

income effect 𝜂≤0

Slutsky equation: εu = εc + η

R

εu

l(w,R) l(w+dw,R)

c=z-T(z) consumption

Page 40: Lecture 4: Optimal Labor Income Taxation · FEDERAL US INCOME TAX US income tax assessed on annual family income (not individual) [most other OECD countries have shifted to individual

General nonlinear income tax

With no taxes: c = z (consumption = earnings)With taxes c = z −T (z) (consumption = earnings - net taxes)T (z) ≥ 0 if individual pays taxes on net, T (z) ≤ 0 if individual receivestransfers on netT ′(z) > 0 reduces net wage rate and reduces labor supply throughsubstitution effectsT (z) > 0 reduces disposable income and increases labor supply throughincome effectsT (z) < 0 increases disposable income and decreases labor supply throughincome effectsTransfer program such that T (z) < 0 and T ′(z) > 0 always discourageslabor supply 40 78

Page 41: Lecture 4: Optimal Labor Income Taxation · FEDERAL US INCOME TAX US income tax assessed on annual family income (not individual) [most other OECD countries have shifted to individual

0 pre-tax earnings z

-T(0)

c=z-T(z) disposable income

slope=1-T’(z)

z*

Effect of Taxes/Transfers on Labor Supply

Page 42: Lecture 4: Optimal Labor Income Taxation · FEDERAL US INCOME TAX US income tax assessed on annual family income (not individual) [most other OECD countries have shifted to individual

0 pre-tax earnings z

-T(0)

slope=1-T’(z)

T(z) < 0: income effect: z decreases

T’(z) > 0: substitution effect: z decreases

z*

Net effect: z decreases

Effect of Taxes/Transfers on Labor Supply (z<z*) c=z-T(z)

disposable income

Page 43: Lecture 4: Optimal Labor Income Taxation · FEDERAL US INCOME TAX US income tax assessed on annual family income (not individual) [most other OECD countries have shifted to individual

0 pre-tax earnings z

-T(0)

slope=1-T’(z)

T(z) > 0: income effect: z increases

T’(z)>0: substitution effect: z decreases

Net effect on z is ambiguous

z*

Effect of Taxes/Transfers on Labor Supply (z>z*) c=z-T(z)

disposable income

Page 44: Lecture 4: Optimal Labor Income Taxation · FEDERAL US INCOME TAX US income tax assessed on annual family income (not individual) [most other OECD countries have shifted to individual

OPTIMAL LINEAR TAX RATE: LAFFER CURVE

c = (1− τ) · z + R with τ linear tax rate and R fixed universal transferfunded by taxes R = τ · Z with Z average earningsIndividual i = 1, ..,N chooses li to max ui ((1− τ) ·wi li + R , li )Labor supply choices li determine individual earnings zi = wi li ⇒ Averageearnings Z =

∑i zi/N depends (positively) on net-of-tax rate 1− τ .

Tax Revenue per person R(τ) = τ · Z (1− τ) is inversely U-shaped with τ :R(τ = 0) = 0 (no taxes) and R(τ = 1) = 0 (nobody works): called theLaffer Curve

44 78

Page 45: Lecture 4: Optimal Labor Income Taxation · FEDERAL US INCOME TAX US income tax assessed on annual family income (not individual) [most other OECD countries have shifted to individual

0

Laffer Curve Tax

Revenue

R

𝜏: Tax Rate

1 𝜏 ∗

R = 𝜏 ∙ 𝑍(1 − 𝜏)

𝜏 ∗ =1

1 + 𝑒 with 𝑒 =

1−𝜏

𝑍∙

𝑑𝑍

𝑑(1−𝜏)

Page 46: Lecture 4: Optimal Labor Income Taxation · FEDERAL US INCOME TAX US income tax assessed on annual family income (not individual) [most other OECD countries have shifted to individual

OPTIMAL LINEAR TAX RATE: LAFFER CURVE

Top of the Laffer Curve is at τ∗ maximizing tax revenue:0 = R ′(τ∗) = Z − τ∗ dZ

d(1− τ) ⇒τ∗

1− τ∗ ·1− τ∗Z

dZ

d(1− τ) = 1

Revenue maximizing tax rate: τ∗ = 11+ e

with e =1− τZ

dZ

d(1− τ)e is the elasticity of average income Z with respect to the net-of-tax rate1− τ [empirically estimable]Inefficient to have τ > τ∗ because decreasing τ would make taxpayersbetter off (they pay less taxes) and would increase tax revenue for thegovernment [and hence univ. transfer R ]If government is Rawlsian (maximizes welfare of the worst-off person withno earnings) then τ∗ = 1/(1+ e) is optimal to make transfer R(τ) as largeas possible 46 78

Page 47: Lecture 4: Optimal Labor Income Taxation · FEDERAL US INCOME TAX US income tax assessed on annual family income (not individual) [most other OECD countries have shifted to individual

OPTIMAL LINEAR TAX RATE: FORMULA

Government chooses τ to maximize utilitarian social welfareSWF =

∑i

ui ((1− τ)wi li + τ · Z (1− τ), li )taking into account that labor supply li responds to taxation and hence thatthis affects the tax revenue per person τ · Z (1− τ) that is redistributedback as transfer to everybodyGovernment first order condition: (using the envelope theorem as limaximizes ui ):

0 =dSWF

dτ =∑i

∂ui∂c ·

[−zi + Z − τ dZ

d(1− τ)

] ,47 78

Page 48: Lecture 4: Optimal Labor Income Taxation · FEDERAL US INCOME TAX US income tax assessed on annual family income (not individual) [most other OECD countries have shifted to individual

OPTIMAL LINEAR TAX RATE: FORMULA

Hence, we have the following optimal linear income tax formulaτ =

1− g

1− g + ewith g =

∑i zi · ∂u

i

∂cZ ·∑

i∂ui∂c

0 ≤ g < 1 as ∂ui∂c is decreasing with zi (marginal utility falls withconsumption)

τ decreases with elasticity e [efficiency] and with parameter g [equity]Formula captures the equity-efficiency trade-off

g is low and τ close to Laffer rate τ∗ = 1/(1+ e) when(a) inequality is high(b) marginal utility decreases fast with income 48 78

Page 49: Lecture 4: Optimal Labor Income Taxation · FEDERAL US INCOME TAX US income tax assessed on annual family income (not individual) [most other OECD countries have shifted to individual

OPTIMAL TOP INCOME TAX RATE(Diamond and Saez JEP’11)

In practice, individual income tax is progressive with brackets withincreasing marginal tax rates. What is the optimal top tax rate?Consider constant MTR τ above fixed z∗. Goal is to derive optimal τIn the US in 2016, τ = 39.6% and z∗ ' $500, 000 (' top 1%).Denote by z average income of top bracket earners [depends on net-of-taxrate 1− τ ], with elasticity e = [(1− τ)/z ] · dz/d(1− τ)

Suppose the government wants to maximize tax revenue collected from topbracket taxpayers (marginal utility of consumption of top 1% earners issmall)49 78

Page 50: Lecture 4: Optimal Labor Income Taxation · FEDERAL US INCOME TAX US income tax assessed on annual family income (not individual) [most other OECD countries have shifted to individual

Optimal Top Income Tax Rate (Mirrlees ’71 model)Disposable

Incomec=z-T(z)

Market income z

Top bracket: Slope 1-τ

z*0

Reform: Slope 1-τ−dτ

z*-T(z*)

Source: Diamond and Saez JEP'11

Page 51: Lecture 4: Optimal Labor Income Taxation · FEDERAL US INCOME TAX US income tax assessed on annual family income (not individual) [most other OECD countries have shifted to individual

Disposable Income

c=z-T(z)

Market income z

z*

z*-T(z*)

0

Optimal Top Income Tax Rate (Mirrlees ’71 model)

Mechanical tax increase:dτ[z-z*]

Behavioral Response tax loss: τ dz = - dτ e z τ/(1-τ)

z

Source: Diamond and Saez JEP'11

Page 52: Lecture 4: Optimal Labor Income Taxation · FEDERAL US INCOME TAX US income tax assessed on annual family income (not individual) [most other OECD countries have shifted to individual

OPTIMAL TOP INCOME TAX RATE

Consider small dτ > 0 reform above z∗.1) Mechanical increase in tax revenue:

dM = [z − z∗]dτ

2) Behavioral response reduces tax revenue:dB = τdz = −τ dz

d(1− τ)dτ = − τ1− τ · e · z · dτ

dM + dB = dτ{[z − z∗]− e

τ1− τ z

}Optimal τ such that dM + dB = 0

⇒ τ1− τ =

1e· z − z∗

z⇒ τ =

11+ a · e with a =

z

z − z∗

52 78

Page 53: Lecture 4: Optimal Labor Income Taxation · FEDERAL US INCOME TAX US income tax assessed on annual family income (not individual) [most other OECD countries have shifted to individual

OPTIMAL TOP INCOME TAX RATE

Optimal top tax rate: τ =1

1+ a · e with a =z

z − z∗

Optimal τ decreases with e [efficiency]Optimal τ decrease with a [thinness of top tail]Empirically a ' 1.5, easy to estimate using distributional dataEmpirically e is harder to estimate [controversial]Example: If e = .25 then τ = 1/(1+ 1.5 · 0.25) = 1/1.75 = 73%

53 78

Page 54: Lecture 4: Optimal Labor Income Taxation · FEDERAL US INCOME TAX US income tax assessed on annual family income (not individual) [most other OECD countries have shifted to individual

REAL VS. TAX AVOIDANCE RESPONSES

Behavioral response to income tax comes not only from reduced laborsupply but from tax avoidance or tax evasionTax avoidance: legal means to reduce tax liability (exploiting tax loopholes)Tax evasion: illegal under-reporting of incomeLabor supply vs. tax avoidance/evasion distinction matters because:1) If people work less when tax rates increase, there is not much thegovernment can do about it2) If people avoid/evade more when tax rates increase, then the govt canreduce tax avoidance/evasion opportunities [closing tax loopholes,broadening the tax base, increasing tax enforcement, etc.]

54 78

Page 55: Lecture 4: Optimal Labor Income Taxation · FEDERAL US INCOME TAX US income tax assessed on annual family income (not individual) [most other OECD countries have shifted to individual

REAL VS. AVOIDANCE RESPONSES

Key policy question: Is it possible to eliminate avoidance responses usingbase broadening, etc.? or would new avoidance schemes keep popping up?a) Some forms of tax avoidance are due to poorly designed tax codes(preferential treatment for some income forms or some deductions)b) Some forms of tax avoidance/evasion can only be addressed withinternational cooperation (off-shore tax evasion in tax havens)c) Some forms of tax avoidance/evasion are due to technological limitationsof tax collection (impossible to tax informal cash businesses)

55 78

Page 56: Lecture 4: Optimal Labor Income Taxation · FEDERAL US INCOME TAX US income tax assessed on annual family income (not individual) [most other OECD countries have shifted to individual

OPTIMAL PROFILE OF TRANSFERS

If individuals respond to taxes only through intensive margin (how muchthey work rather than whether they work), optimal transfer at bottom takesthe form of a “Negative Income Tax”:1) Lumpsum grant −T (0) > 0 for those with no earnings2) High marginal tax rates (MTRs) T ′(z) at the bottom to phase-out thelumpsum grant quicklyIntuition: high MTRs at bottom are efficient because:(a) they target transfers to the most needy(b) earnings at the bottom are low to start with ⇒ intensive labor supplyresponse does not generate large output lossesBut US system with zero MTR at bottom justified if society sees peoplewith zero income as less deserving than average 56 78

Page 57: Lecture 4: Optimal Labor Income Taxation · FEDERAL US INCOME TAX US income tax assessed on annual family income (not individual) [most other OECD countries have shifted to individual

Disposable income

c=z-T(z)

Pre-tax earnings z

45o z*

G

0

Starting from a means-tested program

Page 58: Lecture 4: Optimal Labor Income Taxation · FEDERAL US INCOME TAX US income tax assessed on annual family income (not individual) [most other OECD countries have shifted to individual

Reducing generosity of G and phase-out rate Disposable income

c=z-T(z)

Pre-tax earnings z

45o z*

G

0

Starting from a means-tested program

is desirable if society puts low weight on zero earners

G-dG

=$1 to zero earners less valued than $1 distributed to all

Page 59: Lecture 4: Optimal Labor Income Taxation · FEDERAL US INCOME TAX US income tax assessed on annual family income (not individual) [most other OECD countries have shifted to individual

Reducing generosity of G and phase-out rate Disposable income

c=z-T(z)

Pre-tax earnings z

45o z*

G

0

Starting from a means-tested program

Labor supply response saves government revenue Win-Win reform

is desirable if society puts low weight on zero earners

G-dG

Page 60: Lecture 4: Optimal Labor Income Taxation · FEDERAL US INCOME TAX US income tax assessed on annual family income (not individual) [most other OECD countries have shifted to individual

Optimal Transfers: Participation Responses

Empirical literature shows that participation labor supply responses[whether to work or not] are large at the bottom [much larger and clearerthan intensive responses]Participation depends on participation tax rate:

τp = [T (z)−T (0)]/z

Individual keeps fraction 1− τp of earnings when moving from zeroearnings to earnings z : z −T (z) = −T (0) + z · (1− τp)

Key result: in-work subsidies with T ′(z) < 0 are optimal when laborsupply responses are concentrated along extensive margin and govt caresabout low income workers.60 78

Page 61: Lecture 4: Optimal Labor Income Taxation · FEDERAL US INCOME TAX US income tax assessed on annual family income (not individual) [most other OECD countries have shifted to individual

0 pre-tax income z

-T(0)

𝑐= z-T(z)

(1 − 𝜏𝑝)z

𝜏𝑝=participation tax rate

z

Page 62: Lecture 4: Optimal Labor Income Taxation · FEDERAL US INCOME TAX US income tax assessed on annual family income (not individual) [most other OECD countries have shifted to individual

Starting from a Means-Tested Program

45o

w*

G

0

Pre-tax earnings z

Disposable income

c=z-T(z)

Page 63: Lecture 4: Optimal Labor Income Taxation · FEDERAL US INCOME TAX US income tax assessed on annual family income (not individual) [most other OECD countries have shifted to individual

Introducing a small EITC is desirable for redistribution

45o z*

G

0

Starting from a Means-Tested Program

Pre-tax earnings z

Disposable income

c=z-T(z) if $1 to low paid workers more valued than $1 distributed to all

Page 64: Lecture 4: Optimal Labor Income Taxation · FEDERAL US INCOME TAX US income tax assessed on annual family income (not individual) [most other OECD countries have shifted to individual

Introducing a small EITC is desirable for redistribution

45o z*

G

0

Starting from a Means-Tested Program

Participation response saves government revenue

Pre-tax earnings z

Disposable income

c=z-T(z)

Page 65: Lecture 4: Optimal Labor Income Taxation · FEDERAL US INCOME TAX US income tax assessed on annual family income (not individual) [most other OECD countries have shifted to individual

Introducing a small EITC is desirable for redistribution

45o z*

G

0

Starting from a Means-Tested Program

Participation response saves government revenue

Win-Win reform

Pre-tax earnings z

Disposable income

c=z-T(z)

Page 66: Lecture 4: Optimal Labor Income Taxation · FEDERAL US INCOME TAX US income tax assessed on annual family income (not individual) [most other OECD countries have shifted to individual

Introducing a small EITC is desirable for redistribution

45o z*

G

0

Starting from a Means-Tested Program

Participation response saves government revenue

Win-Win reform If intensive response is small

Pre-tax earnings z

Disposable income

c=z-T(z)

Page 67: Lecture 4: Optimal Labor Income Taxation · FEDERAL US INCOME TAX US income tax assessed on annual family income (not individual) [most other OECD countries have shifted to individual

OPTIMAL PROFILE OF TRANSFERS: SUMMARY

1) If society views zero earners as less deserving than average [conservativeview that substantial fraction of zero earners are “free loaders”] then lowlumpsum grant combined with low phasing out rate at bottom is optimal2) If society views low income workers as more deserving than average[typically bipartisan view] and labor supply responses concentrated alongextensive margin (work vs. not) then low phasing out rate at bottom isoptimal3) Generous lumpsum grant with high MTR at bottom justified only ifsociety views non workers as deserving and no strong response along theextensive margin (work vs. not)

67 78

Page 68: Lecture 4: Optimal Labor Income Taxation · FEDERAL US INCOME TAX US income tax assessed on annual family income (not individual) [most other OECD countries have shifted to individual

ACTUAL TAX/TRANSFER SYSTEMS

1) Means-tested transfer programs used to be of the traditional form withhigh phasing-out rates (sometimes above 100%) ⇒ No incentives to work(even with modest elasticities)Initially designed for groups not expected to work [widows in the US] butlater attracting groups who could potentially work [single mothers]2) In-work benefits have been introduced and expanded in OECD countriessince 1980s (US EITC, UK Family Credit, etc.) and have been politicallysuccessful ⇒ (a) Redistribute to low income workers, (b) improve incentivesto work

68 78

Page 69: Lecture 4: Optimal Labor Income Taxation · FEDERAL US INCOME TAX US income tax assessed on annual family income (not individual) [most other OECD countries have shifted to individual

Debate on Basic Income vs. Means-tested transfer

Basic income definition: all people receive an unconditional sum of money(every year) regardless of how much they earnThis is the R of the linear tax system c = (1− τ) · z + R

Or the −T (0) > 0 of the nonlinear tax system c = z −T (z)

Basic income for everybody + higher taxes to fund it is economicallyequivalent to means-tested transfer phased out with earningsPro basic income: less stigmatizing than means-tested transferCons: basic income requires higher “nominal” taxes (that are then rebatedback)Countries provide “in-kind” basic income in the form of universal healthcare (not the US) and public education 69 78

Page 70: Lecture 4: Optimal Labor Income Taxation · FEDERAL US INCOME TAX US income tax assessed on annual family income (not individual) [most other OECD countries have shifted to individual

0 pre-tax income z

Basic income vs. Means-tested transfer

R

slope=1-τ

Budget: c = (1-τ) z + R

Basic income: give R to all, Tax all earnings z at MTR τ

z*=R/τ

Means-tested transfer: give R to people with z=0, give R-τ z to people with z in (0,z*), Tax earnings z at MTR τ but only above z*

c=z-T(z) disposable income

Page 71: Lecture 4: Optimal Labor Income Taxation · FEDERAL US INCOME TAX US income tax assessed on annual family income (not individual) [most other OECD countries have shifted to individual

IN-KIND REDISTRIBUTION

Most means-tested transfers are in-kind and often rationed (health care,child care, public education, public housing, nutrition subsidies) [care notcash San Francisco reform]1) Rational Individual perspective:

(a) If in-kind transfer is tradeable at market price ⇒ in-kind equivalent tocash(b) If in-kind transfer non-tradeable ⇒ in-kind inferior to cashCash transfer preferable to in-kind transfer from individual perspective

71 78

Page 72: Lecture 4: Optimal Labor Income Taxation · FEDERAL US INCOME TAX US income tax assessed on annual family income (not individual) [most other OECD countries have shifted to individual

IN-KIND REDISTRIBUTION

2) Social perspective: 4 justifications:a) Commodity Egalitarianism: some goods (education, health, shelter, food)seen as rights and ought to be provided to allb) Paternalism: society imposes its preferences on recipients [recipientsprefer cash]c) Behavioral: Recipients do not make choices in their best interests(self-control, myopia) [recipients understand that in-kind is better for them]d) Efficiency: It could be efficient to give in-kind benefits if it can preventthose who don’t really need them from getting them (i.e., force people toqueue to get free soup kitchen)

72 78

Page 73: Lecture 4: Optimal Labor Income Taxation · FEDERAL US INCOME TAX US income tax assessed on annual family income (not individual) [most other OECD countries have shifted to individual

FAMILY TAXATION: MARRIAGE AND CHILDREN

Two important issues in policy debate:1) Marriage: What is the optimal taxation of couples vs. singles?2) Children: What should be the net transfer (transfer or tax reduction) forfamily with children (as a function of family income and structure)?

73 78

Page 74: Lecture 4: Optimal Labor Income Taxation · FEDERAL US INCOME TAX US income tax assessed on annual family income (not individual) [most other OECD countries have shifted to individual

TAXATION OF COUPLES

Three potentially desirable properties:(1) income tax should be based on resources (i.e., family income if familiesfully share their income)(2) income tax should be marriage neutral: no higher/lower tax when twosingle individuals marry(3) income tax should be progressive (i.e., higher incomes pay a largerfraction of their income in taxes)It is impossible to have a tax system that satisfies all 3 conditionssimultaneously:Income tax that is based on family income and marriage neutral has tosatisfy: T (zh + zw ) = T (zh) +T (zw ) and hence be linear i.e. T (z) = τ · z

74 78

Page 75: Lecture 4: Optimal Labor Income Taxation · FEDERAL US INCOME TAX US income tax assessed on annual family income (not individual) [most other OECD countries have shifted to individual

TAXATION OF COUPLES

(1) If couples share their incomes, then family taxation is better. If couplesdon’t share their incomes, then individualized tax is better(2) If marriage responds to tax/transfer differential ⇒ better to reducemarriage penalty, i.e., move toward individualized systemParticularly important when cohabitation is close substitute for marriage(as in Scandinavian countries)(3) If labor supply of secondary earners more elastic than labor supply ofprimary earner ⇒ Secondary earnings should be taxed less(Boskin-Sheshinski JpubE’83)Labor supply elasticity differential between primary and secondary earnersis decreasing over time as earnings gender gap decreases (Blau and Kahn2007)

75 78

Page 76: Lecture 4: Optimal Labor Income Taxation · FEDERAL US INCOME TAX US income tax assessed on annual family income (not individual) [most other OECD countries have shifted to individual

TRANSFERS OR TAX CREDITS FOR CHILDREN

1) Children reduce normalized family income ⇒ Children increasemarginal utility of consumption ⇒ Transfer for children Tkid should bepositiveIn practice, transfers for children are always positive2) Should Tkid (z) increase with income z?Pro: rich spend more on their kids than lower income familiesCons: Lower income families need child transfers mostIn practice, Tkid (z) is fairly constant with z

Europe has much more generous pre-kindergarten child care benefits, UShas more generous cash tax credits for families with children76 78

Page 77: Lecture 4: Optimal Labor Income Taxation · FEDERAL US INCOME TAX US income tax assessed on annual family income (not individual) [most other OECD countries have shifted to individual

REFERENCES

Jonathan Gruber,Public Finance and Public Policy, Fifth Edition, 2016 WorthPublishers, Chapter 20 and Chapter 21Blau, F. and L. Kahn “Changes in the Labor Supply Behavior of Married Women:1980-2000”, Journal of Labor Economics, Vol. 25, 2007, 393-438. (web)Boskin, Michael J., and Eytan Sheshinski. “Optimal tax treatment of the family:Married couples.” Journal of Public Economics 20.3 (1983): 281-297.(web)Diamond, P. and E. Saez “From Basic Research to Policy Recommendations: TheCase for a Progressive Tax”, Journal of Economic Perspectives, 25.4, (2011):165-190. (web)IRS, Statistics of Income Division “U.S. Individual Income Tax: Personal Exemptionsand Lowest and Highest Tax Bracket”(2013) (web)

77 78

Page 78: Lecture 4: Optimal Labor Income Taxation · FEDERAL US INCOME TAX US income tax assessed on annual family income (not individual) [most other OECD countries have shifted to individual

Piketty, Thomas and Emmanuel Saez “Optimal Labor Income Taxation,” Handbookof Public Economics, Volume 5, Amsterdam: Elsevier-North Holland, 2013. (web)Saez, Emmanuel. “Optimal income transfer programs: intensive versus extensivelabor supply responses.” The Quarterly Journal of Economics 117.3 (2002):1039-1073.(web)

78 78