RE: [CTPP] ESRI article on ACS errors

Michael: Short answer: very well. Long answer: The wording on the ACS vehicle availability question is identical to the Census 2000 question. It's placement in the ACS is between the two housing utility questions (plumbing/kitchen/telephone facilities, and home heating), so these are all the "easy" housing questions before one has to answer the "difficult" housing questions (e.g., how much is spent on x, y, and z....) We've done some county and regional level tabulations of our region's auto ownership patterns, from 1960 to 2006, and the trends do make good sense at both the regional and county level. There are some ups-and-downs in the county-level zero vehicle shares, comparing 2000 to 2005 to 2006, but these may not be statistically significant. (We published this data, released in I believe September 2007, for a November 2007 regional workshop, url: http://www.mtc.ca.gov/maps_and_data/datamart/census/) Our regional share of zero-vehicle households has declined from 19.7% in 1960, to 15.8% in 1970; 12.2% in 1980; 10.5% in 1990; 10.0% in 2000; and then 9.5% in 2005, and 9.2% in 2006. This is for the nine-county San Francisco Bay Area. For San Francisco City, the zero-vehicle household share has decreased from 42.1% in 1960; 39.6% in 1970; 34.6% in 1980; 30.7% in 1990; 28.6% in 2000; and then with the ACS: 31.3% in 2005, but dropping back to 28.6% in 2006 (same as 2000). So, we're anxiously awaiting the 2007 annual ACS data that's scheduled for released next month and September, and then the 3-year period estimates (2005-2007) expected this December. The challenge will be how to analyze and report all of this data in a timely manner, all the while trying to do our "regular jobs."....The other challenge: do we just report the estimates WITHOUT their standard errors necessary in understanding the year-to-year, or period-to-period difference; or do we take the EXTRA time needed to report the estimates WITH the standard errors (adding, or perhaps "delaying" the reporting of the results by say 3 to 6 months? Chuck ************************************************************** Charles L. Purvis, AICP Principal Transportation Planner/Analyst Metropolitan Transportation Commission 101 Eighth Street Oakland, CA 94607-4700 (510) 817-5755 (office) (510) 817-7848 (fax) cpurvis(a)mtc.ca.gov (e-mail) www: http://www.mtc.ca.gov/ ************************************************************** Chuck (or others), In your opinion, how well do you think ACS is estimating Zero Vehicle Households? (or conversely household vehicle ownership?) Michael E. Cline Research Associate Institute for Demographic & Socioeconomic Research The University of Texas at San Antonio 1 UTSA Circle BB 4.06.10 San Antonio, TX 78249-0704 (210)458-6537 f(210)458-6541 michael.cline(a)utsa.edu http://idser.utsa.edu