1. The U.S. Census Bureau Population Estimates Program Victoria A. Velkoff U.S. Census Bureau APDU Annual Conference September 25, 2008

2. 2 Outline What population estimates we produce and why Basic methodology and data sources Challenges and special censuses Research we are doing

3. 3 Annual Estimates Population –National by age, sex, race, and Hispanic origin –States by age, sex, race, and Hispanic origin –Counties by age, sex, race, and Hispanic origin –Incorporated places and minor civil divisions (total population only) –Puerto Rico Commonwealth and municipios by age and sex Housing units –States –Counties

4. 4 Why Do We Produce Estimates? Federal Mandate The Intercensal Estimates Program is required under U.S.C. Title 13, Section 181: “During the intervals between each census of population…the Secretary, to the extent feasible, should annually produce and publish for each State, county, and local unit of general purpose government which has a population of fifty thousand or more, current data on total population and population characteristics and, to the extent feasible, shall biennially produce and publish for other local units of general purpose government current data on total population.”

5. 5 Uses of Population Estimates Allocation of over $300 billion in federal funds each year Controls for surveys –Current Population Survey –American Community Survey –Survey of Income and Program Participation –American Housing Survey Denominators for statistical rates –Birth and death rates (NCHS) –Per capita income (BEA) Other Federal Uses and Program Planning –Department of Education, National Cancer Institute –Location of public and private services

6. 6 Current Methods National level: Cohort-component method P 2 = P 1 + B - D + NIM (International Migration) State and county level: Component of change method P 2 = P 1 + B - D + NM (Domestic and International) (controlled to the national estimates) Subcounty level: Distributive housing unit method County population is distributed to subcounty parts based on updated estimates of housing

7. 7 Data Sources for Base Population and Vital Statistics Base population –Latest census in current geography Vital statistics –National Center for Health Statistics (NCHS) –Federal-State Cooperative Program for Population Estimates (FSCPE)

8. 8 Data Sources for Migration Domestic migration –Federal tax returns (IRS) –Medicare International migration –American Community Survey Foreign born net migration Net movement to/from Puerto Rico –Other sources Native emigration

9. 9 Challenges and Special Censuses Challenges –An alternate estimate provided by the governmental unit and accepted by the Census Bureau –Usually based on housing unit data Special Census –A basic enumeration of population, housing units, and group quarters conducted by the Census Bureau for governmental units

10. 10 Housing Unit Method Population t = HU t *PPH t * O t + GQ t Where: HU = Number of housing units PPH = Persons per household O = Occupancy rate (we say vacancy as well) GQ = Group Quarters Population

11. 11 2000-2006 Challenge Results Year Number of accepted challenges 200665 200547 200437 200326 200214 20013

12. Research Efforts in the Population Estimates Program HUBERT - Housing Unit Based Estimates Research Team Current Methodology – Ongoing efforts to improve our current methodology

13. 13 Census Bureau sponsored a data user conference in July 2006 Consider alternative methods and data sources for producing population estimates Emphasis on the housing unit method Research use of the American Community Survey (ACS) and Master Address File (MAF) in population estimates HUBERT Background

14. 14 1.Evaluations and basic comparisons of housing unit method and administrative records (ADREC) method for estimating population 2.Review of current methodology for estimating housing units 3.Research into ways to estimate persons per household (PPH) and vacancy HUBERT Areas of Research

15. 15 HUBERT Topic 1: Evaluation Created a set of county household population estimates using the housing unit method Compared these estimates to Census 2000 Used mean absolute percent error (MAPE), mean algebraic percent error (MALPE) and percent difference as evaluation measures

16. 16 In addition to that evaluation… Evaluated two alternative set of estimates ADREC (the Census Bureau’s 1990s based household population estimates) Average of the two methods Compared MAPEs, MALPEs, and percent differences County size categories County growth between 1990 and 2000

17. 17 Mean Absolute Percent Errors (MAPEs) and Mean Algebraic Percent Errors (MALPEs) MethodMAPEMALPE Housing Unit5.91.4 ADREC3.2-1.5 Average of the two methods3.8-

18. 18 Counties by Which Method Was Closer to Census 2000 ADREC was closer in 70% of counties Method Closer to Census 2000

19. 19 MAPE by Population Change: 1990 to 2000

20. 20 HUBERT Topic 1 Findings ADREC method produced estimates that were closer to Census 2000 for all size and growth categories In 30 percent of counties, the housing unit method was closer to Census 2000 Current estimates of each component (HU, PPH, and Vacancy) are necessary to obtain more accurate Housing Unit-Based estimates

21. 21 Topic 2: Review of Housing Unit Estimates Looked at input for our current housing unit estimates (e.g., housing loss, building permits, etc.) Examined the Master Address File to see if we could use it in our estimates Looked at cadastral (tax assessor) files

22. 22 HUBERT Topic 2 Findings There are regional differences in housing unit loss rates by year-built categories not accounted for in the current methodology for estimating housing unit loss. By excluding specific types of addresses and including others in the MAF extracts, the total number of addresses in the MAF extracts becomes more consistent with the housing unit estimates at the national and county levels.

23. 23 HUBERT Topic 3: Persons per Household and Vacancy We examined using American Community Survey estimates of persons per household and vacancy We also examined using regression models to estimate persons per household and vacancy

24. 24 HUBERT Topic 3 Findings For a large number of counties, the usefulness of the one-year estimates of PPH from the ACS for population estimates is limited by the ACS sample size. As was found in previous research, more accurate estimates of PPH can be obtained through the use of regression models and extrapolations rather than by simply using the values from the previous census.

25. 25 HUBERT Next Steps Production Incorporate new housing unit loss rates into 2009 housing unit estimates Develop strategy to include tallies from the MAF in housing unit estimates review Compare vintage 2008 ADREC method estimates with Housing Unit-based estimates as part of estimates review Continue examination of the ACS as a source of estimates of PPH and occupancy rates

26. 26 Next Steps in Terms of Population Estimates Research Goal – To conduct and document research into the use of multiple methods for producing population estimates so that informed methodological decisions can be made post 2010 Continue to collaborate with our state partners and external stakeholders Look at other methods for population estimates (e.g., ratio correlation) Develop an evaluation plan for population estimates and the 2010 Census

27. 27 Improvements to Current Method Vintage 2007 Changes –Net international migration –Change to person-based migration processing –New data source for military data (DMDC) Vintage 2008/2009 Changes and Research –Birth cohorts since 2000 by race and Hispanic origin –Old-age mortality

28. 28 Summary We produce estimates –disaggregated by age, sex, race, and Hispanic origin –at low levels of geography (e.g., counties) –for many purposes We are researching –alternative methods and data sources for population estimates –improvements to our current method