POST ENUMERATION POST ENUMERATION SURVEYSURVEY

Experiences from IndiaExperiences from India

Post Enumeration Survey (PES) is a Post Enumeration Survey (PES) is a sample survey conducted shortly after sample survey conducted shortly after census for the primary purpose of census for the primary purpose of evaluating the census.evaluating the census.

Helps in identifying areas of deficiencies Helps in identifying areas of deficiencies that would need improvement for that would need improvement for subsequent censuses, such as:subsequent censuses, such as:

concepts and definitions employed, concepts and definitions employed, procedures of enumeration and related procedures of enumeration and related

instructions to the field staff etc,instructions to the field staff etc, areas of under Enumeration and misreporting. areas of under Enumeration and misreporting.

What is PES?

It provides an assessment of the It provides an assessment of the accuracy of the census figures.accuracy of the census figures.

It estimates the magnitude of It estimates the magnitude of Coverage errorCoverage error

Omission (under count) Omission (under count) Duplication (over count) of individuals.Duplication (over count) of individuals.

Content errorContent error Response errors in respect of certain selected Response errors in respect of certain selected

characteristicscharacteristics

Objectives of PES

No precise estimate of the extent of No precise estimate of the extent of error in the census count was ever made error in the census count was ever made till 1941 census (prior to independence).till 1941 census (prior to independence).

Indian Census Organization, since 1951, Indian Census Organization, since 1951, has traditionally been evaluating the has traditionally been evaluating the results of the Population Census results of the Population Census through PES, also called Post through PES, also called Post Enumeration Check (PEC). Enumeration Check (PEC).

No attempts, however, were ever made No attempts, however, were ever made to adjust the census results based on the to adjust the census results based on the PES results.PES results.

PES in India

The PES combines two types of The PES combines two types of matching studiesmatching studies A post-censal matching survey for the A post-censal matching survey for the

purpose of measuring census purpose of measuring census coverage coverage errorerror

A re-interview survey for the purpose of A re-interview survey for the purpose of evaluating the extent of evaluating the extent of content errorcontent error in in the recorded census characteristics of the recorded census characteristics of the population. the population.

Types of studies in PES

In simpler terms, the PES envisages In simpler terms, the PES envisages answers to the following two questions:answers to the following two questions: Coverage ErrorCoverage Error: How accurately has : How accurately has

every individual been enumerated in every individual been enumerated in the Census? (Omission or duplication)the Census? (Omission or duplication)

Content ErrorContent Error: How precisely have : How precisely have the particulars of individuals been the particulars of individuals been recorded in the Census?recorded in the Census?

Types of studies in PES (contd..)

For any study of coverage error, the most For any study of coverage error, the most important item is the instructions issued important item is the instructions issued on ‘whom to enumerate’ in census. on ‘whom to enumerate’ in census.

The coverage error investigated in PES The coverage error investigated in PES consists of two components:consists of two components:

i.i. Type I error: Type I error: Omission or duplication Omission or duplication of persons due to omission or of persons due to omission or duplication of households.duplication of households.

ii.ii. Type II error: Type II error: Omission or duplication Omission or duplication of individuals in enumerated of individuals in enumerated households.households.

What is Coverage Error

The Indian census defines The Indian census defines 4 types4 types of of persons as eligible for enumeration in a persons as eligible for enumeration in a particular household:particular household:

i.i. Persons, who Persons, who normally residenormally reside and are and are presentpresent in that household in that household during the during the entire periodentire period of enumeration i.e. , from of enumeration i.e. , from 99thth February to 28 February to 28thth February (both days February (both days inclusive)inclusive)

ii.ii. Persons, who are known to be Persons, who are known to be normally normally residingresiding and had and had actually stayed during a actually stayed during a part of the enumeration periodpart of the enumeration period (9 (9thth February to 28February to 28thth February) in the February) in the household but are not present at the time household but are not present at the time of enumerationof enumeration

Persons enumerated in Indian Census

iii.iii.Persons, who are known to be Persons, who are known to be normally normally residingresiding in the household and are in the household and are not not present at the time of visitpresent at the time of visit of the census of the census enumerator enumerator but are expected to return by but are expected to return by 2828thth February February

iv.iv. VisitorsVisitors, who are , who are present in the household present in the household at the time of population enumerationat the time of population enumeration and and are are expected to be away from the place of expected to be away from the place of their usual residence during the entire their usual residence during the entire enumeration periodenumeration period. For the purpose of . For the purpose of census enumeration, such visitors are census enumeration, such visitors are enumerated in the household where they enumerated in the household where they are actually found during the enumeration are actually found during the enumeration period provided they have not been period provided they have not been enumerated elsewhereenumerated elsewhere

Persons enumerated in Indian Census (contd..)

Initial Listing to make the list Initial Listing to make the list exhaustive :exhaustive : All the persons in the household at the time All the persons in the household at the time

of PES enumeration (as on the date of PES) of PES enumeration (as on the date of PES) and in addition, any other person during and in addition, any other person during

the reference period of the population the reference period of the population enumeration enumeration

List considered for PES:List considered for PES: persons covered under the four categories persons covered under the four categories

in Census are only considered for the PESin Census are only considered for the PES

Persons enumerated in PES

Possible reasons for coverage Possible reasons for coverage errorerror

Unconventional HousesUnconventional Houses (e.g. garages, (e.g. garages, temples, gurdwaras, school buildings) where people, temples, gurdwaras, school buildings) where people, though not expected to live, do live. though not expected to live, do live.

Locked HousesLocked Houses at the time of census: at the time of census: A A situation observed mostly in urban areas.situation observed mostly in urban areas.

Visitors and domestic servants omittedVisitors and domestic servants omitted due to ignorance of respondents and limited probing due to ignorance of respondents and limited probing by enumerators.by enumerators.

Under-enumeration of rented Under-enumeration of rented households:households: mainly in urban areas mainly in urban areas

Under-enumeration of new born babiesUnder-enumeration of new born babies

Omission

DuplicationDuplication: There may be cases : There may be cases where persons, who usually live at where persons, who usually live at one place have come to visit their one place have come to visit their families at weekend, may also be families at weekend, may also be included in the household unless included in the household unless probed by the enumerator. In fact probed by the enumerator. In fact he/she should be enumerated at he/she should be enumerated at his/her normal place of residence.his/her normal place of residence.

Possible reasons for coverage Possible reasons for coverage errorerror (contd..)(contd..)

PES data collection should take place PES data collection should take place as soon as soon as possible after the Censusas possible after the Census

This is to This is to minimize matching difficulties minimize matching difficulties related to changes in the composition of related to changes in the composition of householdshouseholds between the two dates. between the two dates.

At the same time, there must be enough time At the same time, there must be enough time to retrieve all the Census materials from the to retrieve all the Census materials from the field to field to avoid any contamination between the avoid any contamination between the two operationstwo operations. .

Keeping this in view, PES for the 2001 census Keeping this in view, PES for the 2001 census was conducted in all the states and union was conducted in all the states and union territories between April to July 2001. territories between April to July 2001.

Time of PES data collectionTime of PES data collection

Step 1: Determination of the sample Step 1: Determination of the sample size, sample design and the size, sample design and the Schedules for canvassing. Schedules for canvassing.

Sample size depends onSample size depends on level of dis-aggregation (Level of data level of dis-aggregation (Level of data

presentation)presentation) level of reliability required for analysislevel of reliability required for analysis resource constraintsresource constraints

Preparation of PESPreparation of PES

Based on Based on 1991 PES omission rates and the 1991 PES omission rates and the PRSEPRSE, sample size at the national level was , sample size at the national level was fixed at 3,000 EBsfixed at 3,000 EBs

For estimating coverage error, all the For estimating coverage error, all the 3000 EBs were considered3000 EBs were considered

For estimating content error, 600 EBs For estimating content error, 600 EBs (20% of EBs used to estimate coverage (20% of EBs used to estimate coverage error) were considered. error) were considered.

These EBs were distributed among all the These EBs were distributed among all the 35 States and Union territories in 35 States and Union territories in proportion to their projected population of proportion to their projected population of 20012001

Linear Systematic Sampling within each Linear Systematic Sampling within each stratum (Rural, City & Non-City) was used stratum (Rural, City & Non-City) was used for selection of EBsfor selection of EBs

Sample Size in 2001 PESSample Size in 2001 PES

Organization of PESOrganization of PES Conducted in all the States through Dte. of Conducted in all the States through Dte. of

Census Operations (DCO) or Dte. of Census Operations (DCO) or Dte. of Economics & Statistics (DES)Economics & Statistics (DES)

Uniform one-day training on concept and Uniform one-day training on concept and methodology etc. was imparted to one methodology etc. was imparted to one Nodal Officer from each DCO/DES at ORGINodal Officer from each DCO/DES at ORGI

Nodal officers in turn imparted 2 days Nodal officers in turn imparted 2 days training to their officials training to their officials (Enumerators/Supervisors) for field/desk (Enumerators/Supervisors) for field/desk work and supervision work and supervision

Officials drafted for PES work were not Officials drafted for PES work were not involved in Census data collection involved in Census data collection

Organization of PES Organization of PES contd.contd.

PES work starting from re-listing to field PES work starting from re-listing to field reconciliation: 10 days per Enumeration reconciliation: 10 days per Enumeration Block were considered necessary. Block were considered necessary.

In addition to PES enumerators, PES In addition to PES enumerators, PES supervisors were appointed to supervise supervisors were appointed to supervise the work of enumerators. the work of enumerators. Each supervisor was allotted 5 Enumeration Each supervisor was allotted 5 Enumeration

Blocks.Blocks. Overall monitoring was done by senior Overall monitoring was done by senior

officers of the Census organisation and officers of the Census organisation and State Govts (wherever they were involved State Govts (wherever they were involved in PES work)in PES work)

Data Collection MethodologyData Collection Methodology The unit of analysis in the PES is The unit of analysis in the PES is

person (member of household). person (member of household). The target universe included the The target universe included the

residential and partly-residential residential and partly-residential houses. houses.

Only normal households were Only normal households were covered; institutional and houseless covered; institutional and houseless households were excluded in view of households were excluded in view of its insignificant proportion to total its insignificant proportion to total population. population.

Three main schedules Three main schedules Related to Coverage ErrorRelated to Coverage Error::

Schedule on listing of Building/Census House/ Schedule on listing of Building/Census House/ Households (Schedule-I)Households (Schedule-I): To identify omitted or : To identify omitted or duplicated duplicated householdshouseholds (Type I error) (Type I error)

Schedule on listing of members of the Household Schedule on listing of members of the Household (Schedule-IV)(Schedule-IV): To find out : To find out personspersons omitted or omitted or duplicated in households enumerated in the census duplicated in households enumerated in the census (Total error)(Total error)

Related to Content ErrorRelated to Content Error:: Schedule on individual particulars (Schedule-VI)Schedule on individual particulars (Schedule-VI): :

To determine content error in respect of To determine content error in respect of selected selected questionsquestions like age, sex, marital status, literacy, like age, sex, marital status, literacy, educational level, disability, work and fertility statuseducational level, disability, work and fertility status

Three more Schedules - used for desk matching & field Three more Schedules - used for desk matching & field reconciliationreconciliation

Schedules Canvassed in PESSchedules Canvassed in PES

PES: Stages of workPES: Stages of work

Three distinct stages of operation :Three distinct stages of operation :i.i. Field OperationField Operation:: Independent listing Independent listing

and independent canvassing of the and independent canvassing of the PES Schedules I,IV and VI (wherever PES Schedules I,IV and VI (wherever applicable)applicable)

ii.ii. Desk JobDesk Job:: Desk matching of Desk matching of particulars collected in the PES and particulars collected in the PES and the corresponding Census records of the corresponding Census records of an EBan EB

iii.iii. Field Reconciliation:Field Reconciliation: a field a field operationoperation

Criteria for matching Criteria for matching householdshouseholds

A household was considered as A household was considered as matchedmatched between PES and Census only when the between PES and Census only when the following were same in both PES following were same in both PES Schedule I and Census:Schedule I and Census: house numberhouse number use of the census houseuse of the census house name of the head of the household name of the head of the household

Partially matchedPartially matched case, established at the case, established at the desk match stage, were desk match stage, were probed during probed during field reconciliationfield reconciliation (repeat visit in that (repeat visit in that household) for arriving at a decision household) for arriving at a decision regarding its status as matched or not. regarding its status as matched or not.

In case of persons listed in In case of persons listed in Schedule IVSchedule IV, a match , a match was established at was established at desk matchdesk match stage when all the stage when all the following were same in both the recordsfollowing were same in both the records NameName SexSex relationship to headrelationship to head marital status of the person marital status of the person

The partial match cases were further investigated The partial match cases were further investigated during field reconciliation.during field reconciliation.

Similarly, the entries in PES Schedule VI were Similarly, the entries in PES Schedule VI were matched with the corresponding Census records matched with the corresponding Census records and the partial matched cases were investigated and the partial matched cases were investigated during field reconciliation.during field reconciliation.

Criteria for matching personsCriteria for matching persons

For realistic evaluation of Census, For realistic evaluation of Census, iindependence between the Census and ndependence between the Census and the PES operations is essentialthe PES operations is essential

To maintain independenceTo maintain independence The persons other than Census field The persons other than Census field

functionaries were engaged for PES workfunctionaries were engaged for PES work One group of persons for One group of persons for re-listingre-listing / / re-re-

enumerationenumeration during PES during PES Another group of persons for Another group of persons for desk matchingdesk matching

and and field reconciliationfield reconciliation

Independency of PES from Independency of PES from CensusCensus

Independency of PES from Census Independency of PES from Census contd.contd.

Census enumeration records were brought Census enumeration records were brought to the concerned DCO before to the concerned DCO before commencement of PEScommencement of PES. .

The The list of the selected EBs was not disclosedlist of the selected EBs was not disclosed till the population enumeration was over. till the population enumeration was over. The The Census field staff did not have any prior Census field staff did not have any prior knowledge of the selected EBs of PESknowledge of the selected EBs of PES. .

The Abridged House List (AHL) and filled –in The Abridged House List (AHL) and filled –in Census Household Schedule 2001 were not Census Household Schedule 2001 were not shown to the PES enumeratorshown to the PES enumerator till completion till completion of field work. of field work.

Results of PES 2001Results of PES 2001

Coverage Error:Coverage Error: Omission rate is 24 per 1000 persons at Omission rate is 24 per 1000 persons at

National levelNational level Duplication rate is 1 per 1000 persons at Duplication rate is 1 per 1000 persons at

National levelNational level Net omission rate (NOR) at National level: 23 Net omission rate (NOR) at National level: 23

per 1000 personsper 1000 persons NOR higher in urban areas (40 per 1000 NOR higher in urban areas (40 per 1000

persons) than that of rural areas (17 per 1000 persons) than that of rural areas (17 per 1000 persons)persons)

NOR higher in the age-group of 0-4 and 20-24 NOR higher in the age-group of 0-4 and 20-24 yearsyears

No significant difference in NOR by sexNo significant difference in NOR by sex

Results of PES 2001Results of PES 2001

Content Error:Content Error: Content error is estimated only for matched Content error is estimated only for matched

persons and selected variablespersons and selected variables Indicators of Content ErrorIndicators of Content Error::

Gross Difference Rate: Percentage of persons Gross Difference Rate: Percentage of persons for whom the classification differs both in for whom the classification differs both in Census and PES to total persons with regard to Census and PES to total persons with regard to a variablea variable

Net Difference Rate:Net Difference Rate:

(Value of Census for a characteristic – Value of (Value of Census for a characteristic – Value of PES) x 100PES) x 100

Sample population sizeSample population size Index of inconsistency: Index of inconsistency: It estimates the ratio of It estimates the ratio of

response variance to total variance for a response variance to total variance for a question answer. It is a relative measure of question answer. It is a relative measure of response variance. response variance. <20 (low), 20 to 50(moderate) and <20 (low), 20 to 50(moderate) and >50(high)>50(high)

Results of PES 2001 Results of PES 2001 contd.contd.

Content ErrorContent Error

Characteristic Gross Difference

Rate

Net Difference

Rate

Index of Inconsistenc

y

Persons by marital status

0.3 to 0.9 -0.3 to 0.3 Low ( < 20 )

Persons by Literacy

0.5 to 6.3 -0.8 to 0.1 Low ( < 20 )

Persons by disability

0.3 to 1.6 -1.6 to 1.6 Low ( < 20 )

Persons by work status

0.3 to 1.2 -3.6 to 3.6 Low ( < 20 )

Persons by category of economic activity

0.2 to 0.4 -1.4 to 1.2 Low ( < 20 )

Values shown in ranges are for different sub-groups within Values shown in ranges are for different sub-groups within each characteristiceach characteristic