ACS PUMS – How to Aggregate Sample

1. ACS PUMS – How to Aggregate Sample Anthony Tersine US Census Bureau Census Information Center Meeting October 10, 2007

2. ACS PUMS - Sampling • 2005 PUMS is limited to housing units and household population • 2006 PUMS includes housing units, household population and the group quarters population

3. Multiyear PUMS Files • Two approaches – both combine single year files • Adjust estimates at the end • Adjust weights at the beginning

4. Method 1 • Concatenate single year files • Adjust dollar amounts for inflation • Express prior year dollars in terms of latest year dollars

5. Adjust Dollar Amounts – 1 • First apply “ADJUST” variable within year • Apply the CPI-U-RS adjustment factors from BLS • http://www.bls.gov/cpi/cpiurs1978_2006.pdf

6. Adjust Dollar Amounts – 2 • Express year 2005 dollars in terms of 2006 dollars • Values from the CPI-U-RS table for 2005 (286.7) and 2006 (296.1) • Multiply the 2005 dollars by 296.1/286.7 = 1.03279

7. Adjust Dollar Amounts – Example • 2005-2006 person income in 2006 $ • 2005 person record PINC * (ADJUST / 1000000) * 1.03279 • 2006 person record PINC * (ADJUST / 1000000) • ADJUST – different values

8. Method 1 –Tabulations • Use combined file as a single-year file • Adjust estimates based on number of years (M) combining • Create counts, means, medians, etc. • Create separate estimates for HU and GQ persons • Standard Errors • Replicate weights • Generalized variances

9. Method 1 – Counts / Aggregates • All years have GQs or only interested in HU or household pop

10. Method 1 – Counts / Aggregates • Counts or aggregates - replicates • Counts only - generalized

11. Method 1 – Counts / Aggregates • Some (but not all) years have GQs • M is total number of years • N is the number of years with GQ data

12. Method 1 – Counts / Aggregates • Counts or aggregates – replicates • Counts – generalized

13. Method 1 – Counts Example State of Delaware

14. Method 1 – Ratios • All years have GQs or only interested in HU or household pop

15. Method 1 – Ratios • Replicates • Proportion/percents only - generalized

16. Method 1 – Ratios • Some (but not all) years have GQs • M is total number of years • N is the number of years with GQ data

17. Method 1 – Ratios • Replicates • Proportion/percents only - generalized

18. Method 1 – Medians • All years have GQs or only interested in HU or household pop • Normal median (X) on the combined data • Categorical median (Interpolated)

19. Method 1 – Medians • Replicates • Generalized – Can be done

20. Method 1 – Medians • Some (but not all) years have GQs • Use method 2

21. Method 2 • Concatenate single year files • Adjust weights • Adjust dollar amounts for inflation • Same approach as method 1

22. Adjust Weights • Adjustment factor is the number of years being combined • Divide by the factor

23. Adjust Weights – Example 1 • 2005-2006 Estimate (PWGTP) • 2005 HU person - weight 50 becomes 25 • 2006 HU person - weight 75 becomes 37.5 • 2006 GQ person - weight 60 will stay 60

24. Adjust Weights – Example 2 • 2005-2007 Estimate (PWGTP) • 2005 HU person - weight 67 becomes 22.333333 • 2006 HU person - weight 50 becomes 16.666667 • 2007 HU person - weight 75 becomes 25 • 2006 GQ person - weight 60 becomes 30 • 2007 GQ person - weight 55 becomes 27.5

25. Contact Information Anthony.G.Tersine.Jr@census.gov Alfredo.Navarro@census.gov