Statistics and the Census

1. Statistics and the Census

2. Phases of the “Modern” Census (1990/2000) • “Enumeration” (mail out/mail back) • Non-respondent follow-up (NRFU): complete or sampled(rejected by Congress 2000, not our focus) • Post-enumeration survey (PES, aka ACE): informational purposes or adjustment by ICM/DSE(rejected by Congress 1990, 2000)

3. Capture/recapture (simplified DSE) After the enumeration phases (original plus non-respondent followup), administer PES to a small fraction of the population. Match enumeration results to PES results. Use a simple independence assumption to estimate number of people not included in either enumeration or PES. Adjust census totals using this estimate. (See Mathematica demo) Real DSE divides population into demographic poststrata, much more complicated than this.

4. Potential “errors” due to sampling • Assumes independence that may not exist (e.g., those not enumerated more likely to not be found in PES). • May mismatch enumeration and PES • If too many poststrata, sample sizes may be too small in each stratum, requires some sort of “smoothing” • Assumption of geographic homogeneity within a poststratum • Procedure is so complex that many unpredictable errors are bound to be lurking (Brown and others)

5. Some questions • Should sampling ever be used in a future census? • Since most real-world statistical practices are fraught with potential errors, to the extent that experts can’t agree on what procedure is “best”, how can the public choose a procedure? • How do you feel about technical issues becoming politicized? Is any census question inevitably going to become politicized? • Should scientists always be aware of the political implications of their work? • How can we apply statistics when the basic definitions can’t be agreed on (e.g., race), but most people agree there is something to be fixed (e.g., the differential undercount)?