Coverage Measurement in the 2010 Census (2009) / Chapter Skim
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2 Fundamentals of Coverage Measurement
2 Fundamentals of Coverage Measurement
Pages 15-54
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From page 15... ...
Clearly, the broad goal of measuring the quality of the coverage of the census is to assess the extent of census coverage error by domain and by demographic group. Coverage measurement is a collection of techniques that measure the differences between census enumerations and the corresponding true counts for groups or areas.
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From page 16... ...
We now provide more detail on the nature and causes of these various types of census coverage error. Undercounts Omissions result from a missed address on the decennial census' Master Address File (MAF)
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From page 17... ...
the inclusion of a person at two distinct residences, possibly both of which are part-time residences or because of a move shortly before or shortly after Census Day. Counts in the Wrong Location The two fundamental types of census coverage error, overcounts and omissions (undercounts)
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From page 18... ...
Imputations In addition to census coverage errors that result from the data col lected in the census, there are also enumeration errors that result from the methods, typically imputation, that are used to address census non response. As mentioned in National Research Council (2004a)
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From page 19... ...
The net coverage error or the net undercount, defined as the difference between the census count and the true count for a domain, is therefore a useful assessment of the effect of census coverage error on an aggregate of interest. Net coverage error has two benefits: (1)
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From page 20... ...
Therefore, enu merations in the wrong location should not be interpreted as equivalent to overcounts or omissions. Furthermore, census coverage errors, which we classify as erroneous enumerations, duplicates, omissions, and counts in the wrong place, all have somewhat different causes.
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From page 21... ...
Whether one uses net coverage error or rates of components of census coverage error to represent the quality of the census counts for a domain clearly depends on the analysis that one has in mind. To support as much flexibility in summarization and analysis as possible, information on cen sus coverage error needs to be retained at as basic a level as possible, in addition to the summary tabulations that the Census Bureau provides.
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From page 22... ...
The stated Census Bureau plan that the primary purpose of the cover age measurement program in 2010 would be to measure the components of census coverage error in order to initiate a feedback loop for census process improvement is a substantial innovation. An interesting ques tion is the extent to which a coverage measurement program can be used for this purpose, and a major charge to this panel was to determine the extent to which this new focus of coverage measurement should affect the design of the coverage measurement program and the resulting output and analyses.
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From page 23... ...
. Given this, it is as important as ever for the Census Bureau, in evaluating possible alternative designs for the decennial census, to not only assess the likely impacts on the frequency of components of census coverage error, but also to assess the impacts on differential net coverage error for historically undercounted minority groups.
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From page 24... ...
Although drawing a link between census coverage errors and deficient census processes is a challenging task, the Census Bureau thinks that substantial progress can be made in this direc tion. Therefore, the 2010 coverage measurement program has the goal of identifying the sources of frequent coverage error in the census counts.
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From page 25... ...
The hypothesis is that these imputations systematically underrepresented young children since they were underrepresented in the pool of "donor" households. Although demographic analysis can measure the net undercoverage of these groups, it cannot currently shed further light on the validity of this hypothesis.
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From page 26... ...
However, as can be seen in detail in subsequent chapters, there remain vestiges of the previ ous goals in the design of and the outputs produced for the coverage measurement program in 2010. They include the sample design for the postenumeration survey in 2010, the current focus on the release of census tabulations as the main products of census coverage measurement rather than analytic uses of the collected data and the continued high priority of statistical models for net coverage error (the logistic regression modeling)
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From page 27... ...
The activities of such a group would be focused on analyz ing the data collected from the census, the census coverage measurement program, and the various predictors discussed below. Recommendation 2: The Census Bureau should allocate sufficient resources, including funding and staff, to assemble and support an ongoing intercensal research program on decennial census improve ment.
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From page 28... ...
People who cannot be matched to the census are reinterviewed to make any needed corrections due to discovered errors either in the data collection or the matching. Estimation of Net Coverage Error We start from the implementation of DSE in the 1980 and 1990 cen suses, which formally used the construct of a 2 × 2 contingency table as shown in Table 2-2: • M is the estimate of the number of P-sample persons who match to a census enumeration (within the defined search area)
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From page 29... ...
Then the estimation of census undercoverage using DSE relies on two additional assumptions: (1) that the P-sample enumerations and the census enumerations are independent events, and (2)
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From page 30... ...
in the dual-systems estimate occurs, and its magnitude is a function of the degree to which the individual census enumeration propensities and the individual PES enumeration propensities are correlated. This correlation is small when either the census or the PES enumeration frequencies are relatively con stant; therefore, if DSE is restricted to poststrata in which the people are relatively homogeneous with respect to their enumeration propensi ties, correlation bias will be relatively minor (to see how enumeration heterogeneity can be related to dependence and therefore correlation bias, see Box 2-1)
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From page 31... ...
However, 40 40 27 32 18 23 the equality does not hold for the combined area, since: 10 ≠ 8.6 = 100. 67 72 So capture heterogeneity between Areas A and B has resulted in correlation bias for the combined area.
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From page 32... ...
The number of people that are not data defined, II, is sub tracted from the census count since their match or correct enumeration status cannot be determined. The implicit assumption is that their net c overage error is the same as that for the remaining census enumera This discussion ignores the additional complication raised by the treatment of any late census additions, which are census enumerations that are too late to be included in the dual-systems computations.
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From page 33... ...
What is needed for many applications, rather than estimates of the net coverage error for poststrata, are estimates of the population for small political jurisdictions that are much smaller than the geographic level of the poststrata. In the 1990 and 2000 censuses, synthetic estimation was used for these estimates.
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From page 34... ...
Missing data complicate the application of DSE in the following ways. Although erroneous enumerations in the E-sample that have suf ficient information for matching are typically identified as erroneous (though there are cases for which correct enumeration status has to be imputed)
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From page 35... ...
The difficulty in achieving homogeneity not only reduces the quality of the estimation of the fourth cell, but it also reduces the quality of any small-area estimates of net coverage error produced using synthetic estimation. For duplicates, data-defined enumerations with name and date of birth in the E-sample in the P-sample block clusters are typically discov ered, but duplicates outside the P-sample blocks were either undiscovered and erroneously treated as nonduplicate correct census enumerations or were categorized as erroneous enumerations.
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From page 36... ...
plans to search nationwide for PES matches will be extremely helpful in arriving at a better understanding of the types and frequencies of components of census coverage error. Lastly, errors in geography, or demographics, or other characteristics, can also result in the placement of individuals in the wrong poststratum, which can also bias the estimation of net coverage error.
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From page 37... ...
. Basic Approach Demographic analysis makes use of the following "balancing equation" to estimate the population in a demographic group: PNEW = POLD + B – D + I – E, where by demographic group, we mean in particular groups defined by age, sex, and black or nonblack:
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From page 38... ...
census. In addition to the use of data on births, deaths, and immigration, given their high quality, Medicare enrollment data are now used to esti mate the population aged 65 and older without resorting to the above accounting equation. Unresolved Aspects of Demographic Analysis The logic of demographic analysis requires that the population esti mates constructed from the basic demographic accounting relationship be comparable with the populations measured by the census.
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From page 39... ...
The current demographic analysis program at the Census Bureau also links the measures from the current census with censuses back to 1940. While DSE stands alone as a measure of the coverage of a particular cen sus, the demographic analysis program grounds its current results in the historical data series, so that it is possible to assess one census relative to
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From page 40... ...
The strategy that motivated the post enumeration survey coverage evaluation methodology in the 1950 census was that coverage errors were largely due to failures to correctly implement 10 Again, the realities of the balancing equation provide this linkage. Thus, if current r esearch suggests that the demographic analysis coverage measures for a specific age group need to be adjusted (because, for example, the Medicare data show more or fewer enrollees than expected, or the births for a historical time period appear to be too high, or immigration during a decade had to have been higher or lower)
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From page 41... ...
The results were an estimated net undercount of 1.4 percent, with 2.2 per cent omissions and 0.9 erroneous inclusions. The demographic analysis in 1950 is described in Coale (1955)
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From page 42... ...
(The National Vacancy Check was in some sense the only use of sampling to adjust census counts, by selecting a sample to provide an improved estimate of how many housing units were vacant.) The Census Bureau also carried out two record check studies of specific population groups.
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From page 43... ...
Given this uncertainty, the Census Bureau decided against adjusting the 1980 census for differential net undercoverage. Demographic analysis was also used to estimate the net undercover age of the 1980 census.
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From page 44... ...
Subsequent analysis suggests that the undercoverage of the census was as much as 1.5 percent given reasonable assumptions about the size of the uncounted undocumented population.15 1990 Census Initial plans for the 1990 coverage measurement program were for a PES of 300,000 housing units, which the Census Bureau argued was needed to support net undercoverage estimates (and potentially adjust ment) at the level of geographic aggregation consistent with such uses as reapportionment and redistricting.
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From page 45... ...
However, there was, and still is, no preferred alternative methodology. The Census Bureau released preliminary PES results in April 1991, estimating a national net undercount of 2.1 percent, with a difference of 3.1 percent between the rate of undercoverage of blacks and nonblacks.
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From page 46... ...
This decision required the Census Bureau to greatly modify the design of the 2000 census as well as the associated coverage measurement program. With respect to the census itself, the Census Bureau was not allowed to use sampling for nonresponse follow-up as planned, since that would result in sample-based census counts.
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From page 47... ...
could be demonstrated to provide valid estimates of net coverage error for poststrata and if the estimated net error differed appreciably by poststrata, then adjusted population counts from A.C.E. should be used for redistricting and for other official purposes.
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From page 48... ...
Post-2000 Research A.C.E. Revision I After the 2000 census, the Census Bureau carried out research to investigate the sources and magnitudes of error in the 2000 census, A.C.E., and demographic analysis.
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From page 49... ...
In addition, based on a comparison of the sex ratios from demographic analysis to those from the A.C.E., the Census Bureau decided to revise (increase)
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From page 50... ...
The A.C.E. in the 2000 census was planned from the outset as a method for adjusting census counts for net coverage error so it did not focus on estimating the number or frequency of the various components of census coverage error.
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From page 51... ...
. This method assumes that the net coverage error for women for the relevant demographic group is ignor ably small.
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From page 52... ...
The Role of Demographic Analysis From 1950 through 1980, demographic analysis served as the primary source of estimates of national net coverage error in the decennial census. However, demographic analysis is fundamentally limited: It can only provide estimates of net coverage error for some national demographic groups.
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From page 53... ...
To complete this history of coverage measurement, Table 2-3 shows the national estimates of net coverage error and the estimates disaggregated by black and nonblack for the decennial censuses from 1940 to 2000.
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