Census 2000 -- Scientifically or Politically Correct?

2. Census 2000 -- Scientifically or Politically Correct? Stephen E. Fienberg Departmentof Statistics Notes for Stat 36-149 October, 2001

4. October Census Bureau Decision • March 1, 2001 not to use adjusted data for redistricting. • New October 17 decision against adjustment for intercensal estimates

5. How Many People Were There in the U.S. on April 1, 2000? • At march 1 decision here were the numbers: Raw Census Count: 281.4 million Demographic Analysis: 279.6 million ACE: 284.7 million • Which number should we trust and use? • Should we count or should we estimate?

6. Demographic Analysis • Population = births - deaths + immigration - emigration • only available at national level, and for blacks and whites

7. Net Census Undercount-Mother Rule Undercount Year Black White Differential Net 1940 10.3% 5.1% 5.2% 5.6% 1950 9.6% 3.8% 5.8% 4.4% 1960 8.3% 2.7% 5.6% 3.3% 1970 8.0% 2.2% 5.8% 2.9% 1980* 5.9% 0.7% 5.2% 1.4% 1990** 7.4% 1.0% 6.4% 1.9%

8. Net Census Undercount-Father Rule* Undercount Year Black White Differential Net 1940 8.4% 5.0% 3.4% 5.4% 1950 7.5% 3.8% 3.8% 4.1% 1960 6.6% 2.7% 3.9% 3.1% 1970 6.5% 2.2% 4.3% 2.7% 1980 4.5% 0.8% 3.7% 1.2% 1990 5.7% 1.3% 4.4% 1.8% 2000 -0.65%

9. 2000 DA Census Undercount Estimates (Rev. October 2001) Source Count %Undercount Census 281.4 mil. DA(original) 279.6 mil. -0.65% DA(Alt.March) 282.3 mil. 0.32% DA(Rev. Oct.)* 281.8 mil. 0.12% ACE 284.7 mil. 1.3% *Changes to births and immigration components

10. Demographic Analysis • No reliable measures of uncertainty (variability). • Incompatibilities with new Census race measures. • Major biases for immigration and Hispanics. • Otherwise DA and ACE were much closer than the Bureau admitted! (Passel, 2001)

11. Census Accuracy Myth 3. The ‘actual enumeration’ has been highly successful at counting the population: ‘‘The 1990 census accurately counted 98.4% of the population . . . .” • What is error in the census? • Omissions AND Erroneous Enumerations

12. From A Survey! • Our information about omissions and erroneous enumerations comes from a survey, taken after the census and matched to census records -- the post enumeration survey(PES in 1990 or ACE in 2000).

13. 1990 PES Net Undercount Estimates Group Undercount Differential Non-Black 1.7 Black 4.8 3.1 Hispanic 5.2 3.4 Asian 3.1 1.0 American Indian 5.0 2.9

14. 2000 ACE Net Undercount Estimates Group Undercount Differential Non-Black 1.0 Black 2.1 1.1 Hispanic TBA TBA Asian TBA TBA American Indian TBA TBA

15. Gross vs. Net Error • Omissions • Erroneous Enumerations Gross Error = Omissions + Err. Enumerations Net Error = Omissions - Err. Enumerations • 1990 Gross error (~8-12%) vs. Net error (1.6%)

16. Gross v. Net Error (in millions) 1980 1990___ 2000* erroneous enumerations 6.0 10.3 5.9 omissions 9.2 15.6 9.2 net undercount 3.2 5.3 3.3 gross errors 15.2 25.9 15.1 gross as % of population 7 % 10.4% 5.4% *(based on March, 2001 reports; excludes imputations, suspected duplicates, and group quarter errors)

17. October 17, 2001 Decision • No adjustment for intercensal purposes because of suspected 3 mil. EEs missed by ACE. • Need revised information on gross error but some estimates now put it at 1990 levels, i.e., in neighborhood of 25 million.

18. Sampling and Census 2000 • The Census enumeration Process: • Short Form and Long Form. • Mail-out and mail-back (trying to count all). • Non-response Follow-up. • Institutions and the Homeless. • Accuracy and Coverage Evaluation • Post-Enumeration Survey (314,000 HHs)

19. ACE & Dual Systems Estimation • Survey approximately 314,000 HH in 11,000 blocks. • Correct raw census counts using “capture-recapture” or dual systems methodology. • Corrects for omissions AND erroneous enumerations.

20. Political Bias & Manipulation Myth 6. Census Sampling Would Favor Democrats. “ Statistical errors in the count, accidental or deliberate, could result in as many as 24 GOP seats being lost.” “The ability to ‘create’ or ‘eliminate’ millions of strategically placed citizens with the stroke of a pen introduces a potent and disturbing new political weapon.”

22. Winners and Losers in 1990 and 2000 • 1990 Adjustment winners: • California • Arizona • 1990 Adjustment losers: • Wisconsin • Pennsylvania • In 2000, had adjusted data been used for apportionment, Texas would have gained seat.

24. Perfection of the Sample Myth 11. Persons found in the census but not in the sample are inferred to have been counted erroneously by the census. • ‘Rehnquist-Stark’ fallacy, or “What is dual systems estimation all about?”

26. Dual Systems Components

27. Dual Systems Estimation

28. Dual Systems Example • Counting people in a census block. • 150 people 1st time -- the census; and 200 2nd time -- the sample. • Of 200 people in sample, 125 were among 150 people in the census • Total no. people seen = 200 + (150 - 125) = 225.

29. Example (cont.) • In sample, proportion of people also in census is 125/200, or 5/8. • Generalizing from sample to entire population, we conclude that only 5/8 of people in the block were captured in census: 150 = (5/8) Ñ Ñ = (8/5) (1500) = 240.

30. More Formal Version 125 75 200 25 ? 150 Ñ = 150 200/125 = 240 Ñ = ncen npes/a

31. Dual Systems For Census 2000 • To apply method in the context of ACE, we need to correct census count for EEs by subtracting them. • Practical issues regarding implementation.

32. Dual Systems Assumptions • Perfect matching • Homogeneity • Dependence between sample and census • correlation bias? • Errorless assessment of erroneous enumerations • big issue for 2000 census