RE: [CTPP] 2000 and 2006-08 work trip comparison question.

I would also be interested in a more detailed explanation of why we should not compare overlapping period estimates. From a practical standpoint, people are going to do it anyway, especially the press. What do we need to know - other than the inherent issues of what is a statistically significant vs. insignificant change and the fact that ACS was designed to examine characteristics of the population rather than its level - to be able to correct naïve interpretations of easily calculated tract-level year-to-year differences in the estimates of things like poverty rate, unemployment rate, educational attainment rates, etc.? What is a correct interpretation of these differences? Frank Frank Lenk Director of Research Services Mid-America Regional Council 600 Broadway, Suite 200 Kansas City, MO 64105 www.marc.org<http://www.marc.org> 816.474.4240 flenk@marc.org<mailto:flenk@marc.org> 816.701.8237 From: ctpp-news-bounces(a)chrispy.net [mailto:ctpp-news-bounces@chrispy.net] On Behalf Of Kendra Watkins Sent: Monday, January 31, 2011 10:05 AM To: ctpp-news(a)chrispy.net Subject: RE: [CTPP] 2000 and 2006-08 work trip comparison question. This is interesting. I recall hearing this guidance in the past. However on the Census website on the ACS page it specifically states; "Generally, you can compare American Community Survey (ACS) 3-year and 5-year estimates with Census 2000 data. There are differences in the universe, question wording, residence rules, reference periods, and the way in which the data are tabulated which can impact comparability." The qualifier in the second sentence addresses the conflict (different methods, time periods etc) but I can't find anywhere on the ACS pages where the Census recommends we not compare ACS to decennial Census. And when I search by subject the Journey to Work topic states that I can 'Compare' it to the 2000 Census. It does specifically state not to compare overlapping years on multiyear estimates. Kendra Watkins Senior Data Analyst Mid-Region Council of Governments 809 Copper Ave. NW Albuquerque, NM 87102 Phone: (505)724-3601 Fax: (505)247-1753 Email: kwatkins@mrcog-nm.gov<mailto:tgaudette@mrcog-nm.gov> This email and any files transmitted with it are confidential and intended solely for the use of the individual or entity to which they are addressed. If you have received this email in error please notify the system manager. This message contains confidential information and is intended only for the individual named. If you are not the named addressee you should not disseminate, distribute or copy this e-mail. From: ctpp-news-bounces(a)chrispy.net [mailto:ctpp-news-bounces@chrispy.net] On Behalf Of Weinberger, Penelope Sent: Monday, January 31, 2011 8:41 AM To: ctpp-news(a)chrispy.net Subject: RE: [CTPP] 2000 and 2006-08 work trip comparison question. The CB does not recommend comparing an ACS based data set to a CB Long Form based data set. The 2000 data represent a point in time estimate, the ACS data represent a period estimate. Furthermore, the Census Bureau recommends not comparing period estimates with overlapping years. Penelope Weinberger CTPP Program Manager AASHTO 202-624-3556 http://ctpp.transportation.org/Pages/default.aspx It's just as bad to not make a plan as to blindly follow the one you already have. From: ctpp-news-bounces(a)chrispy.net [mailto:ctpp-news-bounces@chrispy.net] On Behalf Of Seidensticker, Dan Sent: Friday, January 28, 2011 4:18 PM To: (ctpp-news(a)chrispy.net) Subject: [CTPP] 2000 and 2006-08 work trip comparison question. We downloaded the2006-2008 ACS county-to-county worker flow for Dane County, Wisconsin from http://ctpp.transportation.org/Pages/3yrdas.aspx. The question we now have...can that data be compared to the county-to-county 2000 CTPP work trips to determine any statistically significant increase/decrease? If so, how would one calculate the margin of error? Dan Seidensticker GIS Specialist Madison Area Transportation Planning Board: A Metropolitan Planning Organization (MPO) City of Madison Planning Unit 121 S. Pinckney Street, Suite 400 Madison, WI 53703 Voice: 608-266-9119 Fax: 608-261-9967 Email: dseidensticker@cityofmadison.com<mailto:dseidensticker@cityofmadison.com> www.MadisonAreaMPO.org<http://www.madisonareampo.org/>