Re: [CTPP] puma question?

Gustavo: Short answer is no. Long answer is: The place-of-work PUMA (public use microdata area) in the 1990 Census PUMS *should* be county-of-work, in the case of a multi-PUMA county. This is a little disappointing, since we were originally hoping for PUMA-to-PUMA commuter matrices that we could do wonderful things with. The best you can get is a PUMA-to-County commuter matrix, stratified by however you please. (We've done a lot of work with PUMA-to-County data in terms of analyzing the income, means of transportation, race&ethnicity, occupation, sex, age, weight, etc., of "transbay commuters" from the East Bay to San Francisco. Nothing published: just backup factoids as part of our Bay Bridge congestion pricing demo project.) Let's me try to give you a hypothetical example. If your county, say, Harris County, has PUMAs numbered 1801 through 1809, then the PUMA-of-work code is most likely 1800 (equivalent to Harris County-of-work.) Recommend you do a frequency distribution of your POWPUMAs and this logic should hold up. POWPUMAs will nest on your residence PUMAs. I just reviewed the detailed PUMS documentation, and I can't find reference to the issue of how POWPUMAs are coded. One of the problems with PUMS is that PUMA-of-residence is *not* included on the person records; they have to be merged in from the housing unit records. (This is annoying!) Hopefully Phil or Gloria (Census Bureau) will pitch in to correct what I've stated. Or give Phil or Gloria a call. (Gustavo: in your spare time, why don't you do a cross-tab of year of immigration into US by means of transportation to work. Compare to the Los Angeles data shown by Dowell Myers in his article in TRB Conference Proceedings #13, Vol. 2. You may want to anticipate very high transit shares for recent immigrants to the US; and lowest transit shares for older immigrants or native born Americans. I found very similar patterns in the Bay Area as for LA in terms of this relationship. Policy conclusion is that recent immigrants to the US are sustaining public transportation ridership in US metro areas!!! PUMS is great stuff for this type of background research!) Cheers, Chuck Purvis ******************************************************* e-mail: cpurvi(a)mtc.dst.ca.us *or* cpurvi(a)mtc.ca.gov or cpurvis(a)mtc.dst.ca.us *or* cpurvis(a)mtc.ca.gov Chuck Purvis, AICP Senior Transportation Planner/Analyst, Planning Section Metropolitan Transportation Commission 101 Eighth Street, Oakland, CA 94607-4700 (510) 464-7731 (voice) (510) 464-7848 (fax) WWW: http://www.mtc.ca.gov/ (New Address: FEB1398) MTC DataMart & InfoMart: http://www.mtc.ca.gov/facts_and_figures/datamart.htm MTC FTP Site: ftp://ftp.abag.ca.gov/pub/mtc/planning/ Personal WWW: http://home.earthlink.net/~clpurvis/ *******************************************************