RE: [CTPP] RE: TAZ delineation for CTPP (2006-2010) tabulation SCHEDULE

Robert: The income data is tricky in another way: in the past Decennial Census sample data, the question was asked of survey respondents around the time of Census day, April 1. They were asked, what was their income for the previous calendar year? Most people would have just done their income taxes, and would have a pretty reliable idea of their income for that period. Now ACS surveys the population every month of the year, asking what was their income for the prior 12 months, which now most often splits calendar years. Comparisons in 2000 of the Decennial Census Sample Survey versus the ACS method have shown that this new method results in a lower estimate of income than the methodology in the old survey, and I suspect it is because people now are mostly guessing at their income rather than having a precise calculation at hand. Thus income is longitudinally comparable using ACS from one year to the next, but it is not longitudinally comparable using ACS versus 2000 Census. You can expect it to be reasonably comparable horizontally from one neighborhood to another for the same time period. On the other hand, the Great Recession may have affected some neighborhoods more than others, and this may not be captured very well by the long time period represented by the ACS 5-year data. Pete Swensson, Senior Planner Thurston Regional Planning Council 2424 Heritage Ct. SW Olympia, WA 98502 (360) 741-2530 (direct line) (360) 956-7575 (main desk) (360) 956-7815 (fax) swenssp(a)trpc.org This e-mail and any attachments are for the use of the addressed individual. If you have received this e-mail in error, please notify our systems manager. TRPC has taken responsible precautions to ensure no viruses are present in this e-mail, however we do not accept responsibility for loss or damage arising from the use of this e-mail or attachments. From: ctpp-news-bounces(a)chrispy.net [mailto:ctpp-news-bounces@chrispy.net] On Behalf Of Allen, Robert Sent: Monday, October 11, 2010 11:57 AM To: 'ctpp-news(a)chrispy.net' Subject: RE: [CTPP] RE: TAZ delineation for CTPP (2006-2010) tabulationSCHEDULE Pete, Thanks for your reply. I am looking primarily for household incomes as the most urgent data. Income data has always been a notoriously subjective item with wildly varying degrees of reporting accuracy, both intentional and unintentional. I obviously need to do more direct research with the Bureau about the ACS usefulness at various population thresholds. Robert Robert R. Allen, AICP Abilene MPO Transportation Planning Director 400 Oak Street, Suite 102, Abilene, TX 79602 Office (325) 676-6243 Fax (325) 676-6398 Cell (325) 513-4615 ________________________________ From: ctpp-news-bounces(a)chrispy.net [mailto:ctpp-news-bounces@chrispy.net] On Behalf Of Pete Swensson Sent: Monday, October 11, 2010 1:19 PM To: ctpp-news(a)chrispy.net Subject: RE: [CTPP] RE: TAZ delineation for CTPP (2006-2010) tabulation SCHEDULE Robert: Well, the ACS data is what it is - can't get around that. The sample size is smaller than that used for the 2000 Decennial Census sample survey (the equivalent of about 12% versus about 16%), so there are indeed many who are dissatisfied with the resulting higher margin of error. This dissatisfaction is probably increased because Census did not report the margin of error until the ACS came along, in the past allowing Census users (myself included) some degree of blissful ignorance of the actual level of uncertainty. At the small area level, notable error rates actually have been in the sample data all along. Whether it will "not be good" at the block group level will depend on how good it has to be for your purposes, and on what data element you are measuring (e.g., smaller percent margin of error for SOV rates than for bicycle commuters). Block groups are of comparable size nationwide, for small communities and large, ranging in the 2000 Census from about 600 to about 3000 and averaging about 1200 (the 2000 Census geography will be that used in the 2005-09 ACS product). The ACS block group data consequently will be of comparable utility for small communities and large, since it is the size of the block group that counts, not the size of the community. One exception to this rule: Census uses higher sampling rates in low population areas (e.g., small towns and small rural counties) so that they can get a large enough sample to achieve statistical significance when they have to report data for small political jurisdictions. Bottom line: for better or worse, ACS 2005-09 block group data is all we will have in the next few months with small area socio-economic and journey-to-work characteristics, unless one has the resources to do one's own surveys. As Ed Christopher pointed out, the 2010 block data also will be available for our use in delineating new TAZs, though it will be limited to basic demographic information, dwelling counts, and owner vs. renter vs. group quarters. Pete Swensson, Senior Planner Thurston Regional Planning Council 2424 Heritage Ct. SW Olympia, WA 98502 (360) 741-2530 (direct line) (360) 956-7575 (main desk) (360) 956-7815 (fax) swenssp(a)trpc.org This e-mail and any attachments are for the use of the addressed individual. If you have received this e-mail in error, please notify our systems manager. TRPC has taken responsible precautions to ensure no viruses are present in this e-mail, however we do not accept responsibility for loss or damage arising from the use of this e-mail or attachments.