1 The 2010 Census Coverage Measurement Survey Patrick J. Cantwell U.S Census Bureau Annual Meeting of the Association of Public Data Users September 25, 2009

2 Overview Purpose of the 2010 Census Coverage Measurement (CCM) (survey based) Fundamentals of Capture-Recapture Survey design and operations Issues in estimation

3 Introductory Note Several ways to measure coverage of census Post-enumeration survey, CCM Demographic analysis Here, only discuss survey approach

4 Introductory Note (cont.) The basic demographic accounting equation for Demographic Analysis in 2010: Population < 65 (born since 1945) = births – deaths + immigration – emigration Population 65+ = Medicare count + estimated not enrolled Contact: Gregg Robinson, U.S. Census Bureau

5 Purpose of the 2010 CCM No intent to adjust the census counts Estimates of net coverage Estimates of components of census coverage

6 Net Coverage of the 2010 Census Net coverage, including net undercount or overcount, for Key demographic groups Specific geographic areas

7 Components of Census Coverage: Omissions Omissions: – people missed in housing units that are missed – people missed in housing units that are captured

8 Components of Census Coverage: Enumerations Correct Whole-person census imputations ( insufficient information, or II ) Erroneous -- duplicate (issue in 2000) -- should not have been counted -- in the wrong location

9 Components by Census Operations By how we deliver the questionnaire e.g., mail-out/mail-back, update/leave By how census information was captured e.g., mail return, nonresponse follow-up, Be Counted form, etc.

10 Components of Census Coverage Use results to improve future censuses, particularly, 2020 census Help plan upcoming census tests Provide data for evaluations, further studies

11 Capture-Recapture (Gray: Can be measured) Enumerated in PES ? ( P Sample ) YESNOTotal Enumer’d in Census ? ( E sample ) YES N 11 N 12 N 1+ NO N 21 N 22 N 2+ TotalN +1 N +2 N

12 Solve for N Assuming independence...

13 Solve for N But we must sample... dual system estimate:

14 Post-stratification (prior censuses) Why? Concern about “correlation bias”: -- Dependence of two enumerations -- Heterogeneity of capture probabilities Group people with “similar” probabilities of being a correct enumeration or match Estimate p corr enum and p match within group

15 Post-stratification (prior censuses) Within each post-stratum h:

16 Survey Design of 2010 CCM P Sample (independent sample): Sample of people (and housing units) in block clusters E Sample: Census enumerations in the same sample block clusters

17 Sample Design for Independent (P) Sample Sample of block clusters, averaging 30 units As in 2000, exclude remote Alaska and group quarters Stratify by --state, DC, Puerto Rico --American Indian Reservation, size, tenure

18 Sample Design (cont.) Select (end up with) approximately ~ 10,000 block clusters; ~ 500 in Puerto Rico ~ 300,000 housing units; ~ 15,000 in Puerto Rico ~ 700,000 persons

19 CCM Operations and Timing For persons, generally later than in 2000 Why? During the decade of the 2000’s, -- No plan to adjust census counts in Maintain independence between census and CCM operations

20 Sampling and Independent Listing Create block clusters Select block clusters List housing units in independent (P) sample August – December, 2009 Subsample small block clusters

21 Person Interview Conduct interviews and reinterviews: August – October, 2010 Improve CCM person interview and follow-up questionnaires: – additional probes in rostering section – new approach to determine all residences

22 Person Matching Several stages of computer and clerical matching, follow-up, more matching October 2010 – April 2011 In 2000: search for matches limited to sample block cluster and local “search area” In 2010: nation-wide computer matching, to search the census for duplicates

23 Estimation for 2010 CCM Dates of release are still under consideration Estimates from Demographic Analysis may be out near the release of apportionment counts (Dec. 31, 2010) or shortly thereafter Estimates from CCM (survey) will be out sometime in 2012

24 Estimation for 2010 CCM (cont.) Recall: dual system estimator from prior coverage surveys, using post-strata, h:

25 Estimation for 2010 CCM (cont.) In 2000 survey: used 416 post-strata In 2010: predict probabilities using statistical modeling, e.g., logistic regression Hope that these models – will be more efficient – may allow us to include more variables

26 Estimation for 2010 CCM (cont.) Predict (model) probabilities for each person i, rather than for post-strata:

27 Treatment of Movers Want to improve our ability to determine Census Day residence status In 2000 A.C.E.: matching was based on non-movers and out-movers In 2010 CCM: matching will be based on non-movers and in-movers

28 Missing Data In 2000, used hot-deck, selection from distributions, cell imputation In 2010, – for characteristic imputation, use census processing – for other needs, use may statistical modeling (e.g., logistic regression)

29 Estimation Research Transformation(s), variables to use in models Use of splines for age variable Weight trimming for block clusters with outlying statistical results Procedure to reduce correlation bias in our estimates

30 Thank you. Thanks to my co-authors and others who contributed toward this presentation. Contact: