POST ENUMERATION
SURVEY
Experiences from India
What is PES?
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Post Enumeration Survey (PES) is a sample
survey conducted shortly after census for the
primary purpose of evaluating the census.
Helps in identifying areas of deficiencies that
would need improvement for subsequent
censuses, such as:
concepts and definitions employed,
 procedures of enumeration and related instructions to the
field staff etc,
 areas of under Enumeration and misreporting.
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Objectives of PES
It provides an assessment of the accuracy of
the census figures.
 It estimates the magnitude of
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Coverage error
Omission (under count)
 Duplication (over count) of individuals.
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Content error
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Response errors in respect of certain selected characteristics
PES in India
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No precise estimate of the extent of error in the
census count was ever made till 1941 census
(prior to independence).
Indian Census Organization, since 1951, has
traditionally been evaluating the results of the
Population Census through PES, also called
Post Enumeration Check (PEC).
No attempts, however, were ever made to adjust
the census results based on the PES results.
Types of studies in PES
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The PES combines two types of matching
studies
A post-censal matching survey for the purpose of
measuring census coverage error
 A re-interview survey for the purpose of evaluating
the extent of content error in the recorded census
characteristics of the population.
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Types of studies in PES (contd..)
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In simpler terms, the PES envisages answers to
the following two questions:
 Coverage Error: How accurately has every
individual been enumerated in the Census?
(Omission or duplication)
 Content Error: How precisely have the
particulars of individuals been recorded in the
Census?
What is Coverage Error
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For any study of coverage error, the most
important item is the instructions issued on
‘whom to enumerate’ in census.
The coverage error investigated in PES
consists of two components:
i. Type I error: Omission or duplication of
persons due to omission or duplication of
households.
ii. Type II error: Omission or duplication of
individuals in enumerated households.
Persons enumerated in Indian Census
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The Indian census defines 4 types of persons as
eligible for enumeration in a particular household:
i. Persons, who normally reside and are present in
that household during the entire period of
enumeration i.e. , from 9th February to 28th
February (both days inclusive)
ii. Persons, who are known to be normally residing
and had actually stayed during a part of the
enumeration period (9th February to 28th
February) in the household but are not present at
the time of enumeration
Persons enumerated in Indian Census (contd..)
iii. Persons, who are known to be normally
residing in the household and are not present at
the time of visit of the census enumerator but
are expected to return by 28th February
iv. Visitors, who are present in the household at
the time of population enumeration and are
expected to be away from the place of their
usual residence during the entire enumeration
period. For the purpose of census enumeration,
such visitors are enumerated in the household
where they are actually found during the
enumeration period provided they have not
been enumerated elsewhere
Persons enumerated in PES
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Initial Listing to make the list exhaustive :
All the persons in the household at the time of PES
enumeration (as on the date of PES)
 and in addition, any other person during the
reference period of the population enumeration
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List considered for PES:
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persons covered under the four categories in Census
are only considered for the PES
Possible reasons for coverage error
Omission
 Unconventional Houses (e.g. garages, temples,
gurdwaras, school buildings) where people, though not expected
to live, do live.
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Locked Houses at the time of census: A situation
observed mostly in urban areas.
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Visitors and domestic servants omitted due to
ignorance of respondents and limited probing by enumerators.
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Under-enumeration of rented households: mainly
in urban areas
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Under-enumeration of new born babies
Possible reasons for coverage error (contd..)
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Duplication: There may be cases where persons,
who usually live at one place have come to visit
their families at weekend, may also be included
in the household unless probed by the
enumerator. In fact he/she should be
enumerated at his/her normal place of
residence.
Time of PES data collection
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PES data collection should take place as soon as
possible after the Census
This is to minimize matching difficulties related to
changes in the composition of households between the
two dates.
At the same time, there must be enough time to retrieve
all the Census materials from the field to avoid any
contamination between the two operations.
Keeping this in view, PES for the 2001 census was
conducted in all the states and union territories between
April to July 2001.
Preparation of PES
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Step 1: Determination of the sample size, sample
design and the Schedules for canvassing.
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Sample size depends on
level of dis-aggregation (Level of data presentation)
 level of reliability required for analysis
 resource constraints
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Sample Size in 2001 PES
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Based on 1991 PES omission rates and the PRSE,
sample size at the national level was fixed at 3,000
EBs
For estimating coverage error, all the 3000 EBs
were considered
For estimating content error, 600 EBs (20% of EBs
used to estimate coverage error) were considered.
These EBs were distributed among all the 35 States
and Union territories in proportion to their
projected population of 2001
Linear Systematic Sampling within each stratum
(Rural, City & Non-City) was used for selection of
EBs
Organization of PES
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Conducted in all the States through Dte. of Census
Operations (DCO) or Dte. of Economics & Statistics
(DES)
Uniform one-day training on concept and
methodology etc. was imparted to one Nodal Officer
from each DCO/DES at ORGI
Nodal officers in turn imparted 2 days training to their
officials (Enumerators/Supervisors) for field/desk
work and supervision
Officials drafted for PES work were not involved in
Census data collection
Organization of PES
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PES work starting from re-listing to field
reconciliation: 10 days per Enumeration Block were
considered necessary.
In addition to PES enumerators, PES supervisors
were appointed to supervise the work of
enumerators.
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contd.
Each supervisor was allotted 5 Enumeration Blocks.
Overall monitoring was done by senior officers of
the Census organisation and State Govts (wherever
they were involved in PES work)
Data Collection Methodology
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The unit of analysis in the PES is person
(member of household).
The target universe included the residential and
partly-residential houses.
Only normal households were covered;
institutional and houseless households were
excluded in view of its insignificant proportion
to total population.
Schedules Canvassed in PES
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Three main schedules
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Related to Coverage Error:
Schedule on listing of Building/Census House/
Households (Schedule-I): To identify omitted or duplicated
households (Type I error)
 Schedule on listing of members of the Household
(Schedule-IV): To find out persons omitted or duplicated in
households enumerated in the census (Total error)
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Related to Content Error:
Schedule on individual particulars (Schedule-VI): To
determine content error in respect of selected questions like
age, sex, marital status, literacy, educational level, disability, work
and fertility status
Three more Schedules - used for desk matching & field reconciliation
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PES: Stages of work
Three distinct stages of operation :
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i.
Field Operation: Independent listing and
independent canvassing of the PES Schedules I,IV
and VI (wherever applicable)
ii. Desk Job: Desk matching of particulars collected
in the PES and the corresponding Census records
of an EB
iii. Field Reconciliation: a field operation
Criteria for matching households
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A household was considered as matched between PES
and Census only when the following were same in both
PES Schedule I and Census:
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house number
use of the census house
name of the head of the household
Partially matched case, established at the desk match
stage, were probed during field reconciliation (repeat
visit in that household) for arriving at a decision
regarding its status as matched or not.
Criteria for matching persons
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In case of persons listed in Schedule IV, a match was
established at desk match stage when all the following were
same in both the records
 Name
 Sex
 relationship to head
 marital status of the person
The partial match cases were further investigated during
field reconciliation.
Similarly, the entries in PES Schedule VI were matched with
the corresponding Census records and the partial matched
cases were investigated during field reconciliation.
Independency of PES from Census
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For realistic evaluation of Census, independence
between the Census and the PES operations is
essential
To maintain independence
The persons other than Census field functionaries were
engaged for PES work
 One group of persons for re-listing / re-enumeration
during PES
 Another group of persons for desk matching and field
reconciliation
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Independency of PES from Census contd.
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Census enumeration records were brought to the
concerned DCO before commencement of PES.
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The list of the selected EBs was not disclosed till the
population enumeration was over. The Census field
staff did not have any prior knowledge of the
selected EBs of PES.
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The Abridged House List (AHL) and filled –in
Census Household Schedule 2001 were not shown
to the PES enumerator till completion of field work.
Results of PES 2001
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Coverage Error:
 Omission rate is 24 per 1000 persons at National level
 Duplication rate is 1 per 1000 persons at National level
 Net omission rate (NOR) at National level: 23 per
1000 persons
 NOR higher in urban areas (40 per 1000 persons) than
that of rural areas (17 per 1000 persons)
 NOR higher in the age-group of 0-4 and 20-24 years
 No significant difference in NOR by sex
Results of PES 2001
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Content Error:
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Content error is estimated only for matched persons and
selected variables
Indicators of Content Error:
Gross Difference Rate: Percentage of persons for whom the
classification differs both in Census and PES to total persons
with regard to a variable
 Net Difference Rate:
(Value of Census for a characteristic – Value of PES) x 100
Sample population size
 Index of inconsistency: It estimates the ratio of response
variance to total variance for a question answer. It is a relative
measure of response variance. <20 (low), 20 to 50(moderate) and >50(high)
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Results of PES 2001 contd.
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Content Error
Characteristic
Gross Difference
Rate
Net Difference
Rate
Index of
Inconsistency
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 each characteristic