The American Community Survey in Context Presentation Outline

1. What the American Community SurveyCAN and CAN’TTell Us About Local Housing MarketsAPDU ConferenceSeptember 24, 2008Danilo Pelletiere(with Keith Wardrip)National Low Income Housing Coalitionwww.nlihc.org(202) 662-1530 ext. 237

2. The American Community Survey in ContextPresentation Outline • ACS and the decennial census • Other housing surveys • Focus on comparisons to the American Housing Survey and Housing Vacancy Survey • Pitfalls for those familiar with the decennial census • Examples of NLIHC use of ACS Public Use Micro Sample (PUMS) data • Conclusions

3. Old School: The American Housing Survey Data Collection and Sample Size • 55,000 housing units are surveyed as a panel • Lowest geography is census region and select metros and “zones” • National conducted biennially, metros every six years Subjects covered • The AHS asks hundreds of questions about the housing units it samples, including neighborhood and household characteristics. AHS Data Product • A paper report • SAS Microdata with file flattener (Why no flat file?) • Housing Affordability Data System (HADS) Release Schedule • Every two years with a year lag from collection Status • Funding threatened

4. Old School: The Housing Vacancy Survey (Current Population Survey) Data Collection and Sample Size • Supplement to the CPS • About 71,000 addresses per month. A unit is in sample for 4 consecutive months, out for 8 months, back in sample for 4 months, and then retired from the sample. • Lowest geography is 75 largest metros. Subjects covered • Housing tenure, vacancy status, for sale or for rent status, basic householder characteristics AHS Data Product • Press release, historical tables, (cps microdata) Release Schedule • Quarterly and annual statistics Status • No known threat

5. Data Collection and Sample Size • 250,000 surveys distributed monthly; 1 in 40 households each year • Over 5 years, 1 in 8 households will be surveyed, which is comparable to the census long form that the ACS replaces (1 in 6 every 10th year) • ACS Data Products • Data profiles, detailed tables, Public Use Microdata Sample (PUMS) files • Release Schedule • August: income, earnings & poverty data, released with CPS • Yesterday: one-year estimates and PUMS files • December: three-year estimates • Status • Funding threatened New School: American Community Survey

6. The following data are available for Data Profiles and Detailed Tables American Community Survey Basics 1 = 1-year estimate; 3 & 5 are averages based on that many years of data collection

7. Very Useful Housing Data • Cost: contract and gross rent; mortgage payments; specific utility payments; mobile home fees; homeowner association dues; ratio of housing costs to income • Quality: complete plumbing/kitchen facilities; year structure built • Unit/Property: vacancy; value; bedrooms; # of units in structure • Demographics: tenure; income; family type; size; employment status, race and ethnicity • Relationship to other surveys • Better for characteristics, not population counts (Census estimates used for control totals) • Comparability (changes in methods and questions over years and with decennial census) American Community Survey Basics

8. A Comparability Example: What’s Vacant? What’s your primary residence? • ACS uses “current” residence definition and asks if you have lived or will live in a unit for at least two months (2 month rule) • It is asked continuously and vacant units will only be identified in the third month after a survey is sent. • There is a two month window for a property to be occupied, and • A theoretical chance a household will be interviewed at more than one location • Other surveys are “point in time” and ask if the home they are being reached at is the respondent’s “usual” residence.

9. 2005 ACS Housing Estimates Belsky, Drew, and McCue (2007)

10. Difference from the ACS Belsky, Drew, and McCue (2007)

11. If you are Used to the Decennial Census…Estimates can be difficult to interpret • Because the sample is smaller than the decennial census “long form” • analysts must be more careful to determine whether estimates are really “different” from estimates from other populations/geographies. • And because releases are also annual • analysts must be more careful about whether estimates are really “different” from estimates from previous surveys.

12. If you are Used to the Decennial Census…Estimates can be difficult to interpret (cont.) Margin of Error Increases as Size Decreases

13. If you are Used to the Decennial Census…Estimates can be difficult to interpret (cont.) • This is a particular problem in the PUMS where census provides fairly cursory guidance on calculating standard errors and the use of design factors and replicate weights Calculating the margin of error for a “total” estimated from the PUMS file Testing for significance, Census suggests using z values to test for significance Census provides design factors in PDF but provides little guidance on their use.

14. Census versus ACS Housing Data Pitfall Example #2 Three and Five Year Estimates can be Confounding • Time sensitive • What is a local vacancy rate, or a median rent based on three or five years of data worth? • Creates new trade-offs for administrative data • More timely but less local basis for estimating Fair Market Rents, and income limits, • Comprehensive Housing Affordability Strategy data needs local estimates of supply and demand, which make little sense in a three to five year context.

15. If you are Used to the Decennial Census…Remember it is a New Survey. • There are still some kinks to be worked out… • Selected monthly owner costs mistakenly exclude mobile home site rent and related fees for 3.5 million households. This exclusion suppresses the housing cost to income ratio in the PUMS file for 2.8 million of these households.

16. Select Findings from the NLIHC 2006 PUMS Housing FileBased on State Median Family Income Comparison of Units’ Costs with Households’ Ability to Afford Them

17. Select Findings from the NLIHC 2006 PUMS Housing FileBased on State Median Family Income Level of Cost Burden by Tenure and Income Category in California

18. Select Findings from the NLIHC 2005 PUMS Housing FileBased on State Median Family Income

19. Conclusion • The ACS is extremely welcome, providing timely and useful basic housing information, from a large national sample. • It contains similar data to recent decennial censuses • It is much more timely than the decennial census • It’s sample is not as large as the old decennial “long form” • It will help keep track of changing local patterns and trends in basic housing variables better than any existing data set, but analysts must recognize, • It has a larger sample than any other survey except the decennial census • It is not as timely as the Housing Vacancy Survey, • It does not provide the richness of data of the American Housing Survey. • It complements and does not replace these other sources

20. Census and Other ACS Resources Belsky, E.S.; Drew R.B., and McCue, D. (2007) Projecting the Underlying Demand for New Housing Units: Inferences from the Past, Assumptions about the Future. Cambridge, MA: Joint Center for Housing Studies Harvard University. Working Paper W07-7. The American Community Survey website is http://www.census.gov/acs/www/. There is also a chart that discusses the comparability of 2006 ACS data with data from 2005 and the decennial Census, available at http://www.census.gov/acs/www/UseData/compACS.htm. The Missouri Census Data Center provides a very thorough overview of ACS data at http://mcdc2.missouri.edu/pub/data/acs/Readme.shtml. A more complete discussion of pitfall #3 in this presentation can be found in Wardrip, K.E., & Pelletiere, D. (2008). Fully Utilizing Housing Cost Data in the American Community Survey PUMS Data: Identifying Issues and Proposing Solutions. Cityscape, 10, 331-340. For more examples of how American Community Survey data can be used to study housing markets, see the Research Reports and Notes published by NLIHC and available at http://www.nlihc.org/template/page.cfm?id=21.