[CTPP] RE: ctpp-news Digest, Vol 84, Issue 5

Change is "part and parcel" of why we do all of this analysis and data collection. To some degree it is to understand today (not easy given the lags in data collection vs. reporting timeframes) but it is more important for most planning-related work to understand how changes are likely to play out. Understanding trends and dynamics is why we do what we do- at least those of us in the forecasting world. Some places use longitudinal panel surveys to inform forecasting- a very useful albeit expensive approach to develop an understanding of forecasting likely changes. Digging around in the multi-year data sounds like an excellent and perhaps low-cost way to add even more insight to understanding the dynamics of change- even if you can't get a statistically valid measure for every variable/geography in there. Chiming in with Ken C., that too should somehow fit into the overall research plan if we're going to maximize our "return on investment" on the multi-year survey data sets. I guess I'm up to a quarter's worth of thoughts now (or at least a nickel). W -----Original Message----- From: ctpp-news-bounces(a)chrispy.net [mailto:ctpp-news-bounces@chrispy.net] On Behalf Of ctpp-news-request(a)chrispy.net Sent: Tuesday, February 01, 2011 4:26 PM To: ctpp-news(a)chrispy.net Subject: ctpp-news Digest, Vol 84, Issue 5 Send ctpp-news mailing list submissions to ctpp-news(a)chrispy.net To subscribe or unsubscribe via the World Wide Web, visit http://www.chrispy.net/mailman/listinfo/ctpp-news or, via email, send a message with subject or body 'help' to ctpp-news-request(a)chrispy.net You can reach the person managing the list at ctpp-news-owner(a)chrispy.net When replying, please edit your Subject line so it is more specific than "Re: Contents of ctpp-news digest..." Today's Topics: 1. Re: 2000 and 2006-08 work trip comparison question. (Ed Christopher) 2. RE: 2000 and 2006-08 work trip comparison question. (Planning Department) ---------------------------------------------------------------------- Message: 1 Date: Tue, 01 Feb 2011 14:53:19 -0600 From: Ed Christopher &lt;edc(a)berwyned.com&gt; Subject: Re: [CTPP] 2000 and 2006-08 work trip comparison question. To: ctpp-news(a)chrispy.net Message-ID: &lt;4D4872BF.7040902(a)berwyned.com&gt; Content-Type: text/plain; charset=ISO-8859-1; format=flowed Frank-I totally agree and I would like to see the statisticians get involved and think about this. People are going to compare overlapping periods and we have to get smart about how to deal with this. As for why some say we should not compare overlapping years the story goes like this. If you have 2006 to 2008 data and 2007 to 2009 data you would have two overlapping years. According to the logic you would in fact only be comparing the first year 2006 to the last year 2009 as the middle two years would cancel themselves out. While this sounds logical on the surface there has to be a way to deal with overlapping 5-year periods or it doesn't make sense to have an ACS. I am not sure if anyone would out right admit it but is anyone designing performance measures or other regional metrics calling for tracking annual multi-year period estimates at tracts or places? Frank Lenk wrote: 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 naove 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? On Behalf Of Kendra Watkins 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." 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. estimates. 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. On Behalf Of Weinberger, Penelope 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. already have. On Behalf Of Seidensticker, Dan County, Wisconsin from http://ctpp.transportation.org/Pages/3yrdas.aspx. county-to-county 2000 CTPP work trips to determine any statistically significant increase/decrease? If so, how would one calculate the margin of error? dseidensticker@cityofmadison.com<mailto:dseidensticker@cityofmadison.com> -- Ed Christopher 708-283-3534 (V) 708-574-8131 (cell) FHWA RC-TST-PLN 4749 Lincoln Mall Drive, Suite 600 Matteson, IL 60443 ------------------------------ Message: 2 Date: Tue, 1 Feb 2011 15:05:03 -0500 From: Planning Department &lt;PlanningDepartment(a)countyofberks.com&gt; Subject: RE: [CTPP] 2000 and 2006-08 work trip comparison question. To: &quot;ctpp-news(a)chrispy.net&quot; &lt;ctpp-news(a)chrispy.net&gt; Message-ID: &lt;D465CB8E9BCA0249BB15FC9E59276F33A658EDC922(a)MSCLS001.countyofberks.com&gt; Content-Type: text/plain; charset="iso-8859-1" Frank: I agree wholeheartedly with your concerns. One particular issue that we, as data 'superusers' need to remember, is every federal, state, and nonprofit application for aid, grants, loans, etc. will still ask for the same information for a set time. The vast majority of people are still--and will be for a long time--used to using data derived from a "point in time snapshot". Getting us used to working with 'trends' and 'characteristics' has been difficult enough. We now have to pass that knowledge and practice onto those to whom we give that data, whether it be the press, elected officials, nonprofit agencies, students, or the general public. This goes beyond our transportation uses, but at the same time has a significant impact on our transportation uses of these data. Michael D. Golembiewski Transportation Modeler BERKS COUNTY PLANNING COMMISSION 633 Court Street FL 14 Reading, PA 19601 Ph: 610 478-6300 ext 6304 Fax: 610 478-6316 e-mail: mgolembiewski@countyofberks.com<mailto:mgolembiewski@countyofberks.com> Web: http://www.co.berks.pa.us/dept/planning Note: The comments on and attachment to this e-mail are intended only for the use of the individual or entity to which it is addressed, and may contain information that is privileged, confidential and exempt from disclosure under applicable law. If the reader of this message is not the intended recipient, your are hereby notified that any dissemination, distribution or copying of this communication is strictly prohibited. If you received this in error, please contact the sender and delete the original message, any attachment(s) and copies. Thank you for your cooperation. ________________________________ From: ctpp-news-bounces(a)chrispy.net [mailto:ctpp-news-bounces@chrispy.net] On Behalf Of Frank Lenk Sent: Tuesday, February 01, 2011 2:30 PM To: ctpp-news(a)chrispy.net Subject: 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 naove 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/>