[CTPP News] Re: Use of overlapping ACS data

On Mar 16, 2022, at 1:53 PM, David Heller <dheller(a)sjtpo.org> wrote:  Hello: I am still a little confused why using overlapping ACS datasets is not good practice. Can someone explain it to me? Thank you. David Heller, PP/AICP Program Manager - Systems Performance and Subregional Programs South Jersey Transportation Planning Organization 782 S Brewster Road, Unit B6 Vineland, New Jersey 08361 (856) 794-1941 | www.sjtpo.org From: Benjamin Gruswitz <bgruswitz(a)dvrpc.org> Sent: Tuesday, March 15, 2022 4:59 PM To: The Census Transportation Products Program Community of Practice/Users discussion and news list <ctpp(a)listserv.transportation.org> Subject: [CTPP News] Re: CTPP commuter flows in strong MCD states (Vermont test case) Yes, Chuck, this is a data advantage for strong MCD regions--the workplace allocation is complete at this subcounty level that covers all areas of each county (as opposed to place, which doesn't have county-wide coverage). And our TAZs nest within our municipal boundaries, so fitting their flows to the MCD total is a good way to go for adjustments. The only issue in our region is that Philadelphia is both a county and MCD, so we don't get a subcounty control for our TAZ workplace fitting within our high pop/high employment urban center the way we do for our smallest boroughs and townships (we have one borough with a population of 10 and employment of 25). Thanks for always pointing us to good resources and encouraging our experienced and burgeoning R users to explore CTPP data with that toolset! Ben Working from Home | 301.655.3170 Ben Gruswitz, AICP | Manager, Socioeconomic & Land Use Analytics (Pronouns: he/him) Delaware Valley Regional Planning Commission 190 N Independence Mall West, 8th Floor Philadelphia, PA 19106-1520 215.238.2882 | www.dvrpc.org Subscribe | Facebook | Twitter | Instagram | LinkedIn | YouTube On Tue, Mar 15, 2022 at 4:05 PM Charles Purvis <clpurvis(a)att.net> wrote: Being a west coaster, I rarely dabble in MCDs - Minor Civil Divisions, or NECTAs (New England City and Town Areas). I thought this deserves some exploration. I created a new version of my R-package CTPPr script that pulls in intra-state Vermont total commuters: county-to-county, tract-to-tract, and MCD-to-MCD. I’ve shared my Vermont code on my GIST GITHUB. I screwed up yesterday, and had the other scripts in “secret” mode. Oops, sorry. I’ve made the correction. https://gist.github.com/chuckpurvis There are 14 counties in Vermont, 184 census tracts, and 255 MCDs (towns) in Vermont. The 255 MCDs are “wall-to-wall” coverage of the entire state (i.e., no lingering unincorporated “balance of county” areas.) I was surprised that there are fewer census tracts than MCDs in Vermont, but I had some notion that the MCD-to-MCD flow data could be quite valuable (in certain states!) According to the CTPPr documentation, probably the official CTPP documentation, as well, there are MCD-to-MCD commuter flows for the twelve “strong MCD” states. From some random US Treasury document: "Since the government services provided by MCDs differ greatly by state, the Census Bureau refers to twelve states with MCDs that generally provide a wide range of general government services as “strong- MCD” states. In these states, MCDs are generally are treated as municipalities according to state statutes and codes. In eight other states, MCDs typically play less of a governmental role and provide more limited government services, even though they are still active governments (“weak-MCD” states). The twelve strong-MCD states are Connecticut, Maine, Massachusetts, Michigan, Minnesota, New Hampshire, New Jersey, New York, Pennsylvania, Rhode Island, Vermont, and Wisconsin. The eight weak-MCD states are Illinois, Indiana, Kansas, Missouri, Nebraska, North Dakota, Ohio, and South Dakota." Here are the highlights of this Vermont test case: Total Workers, Intra-State, Vermont: County-to-County = 298,422 total workers MCD-to-MCD = 299,415 total workers tract-to-tract = 214,970 total workers. The county-to-county and MCD-to-MCD totals for Vermont should be very, very close, since they both have the “standard allocation procedures” that the Census Bureau uses to impute missing workplace to the county and place level. I’m pretty sure the difference between county-to-county and MCD-to-MCD is rounding issues? Can never tell. The tract-to-tract file does not have the standard allocation procedures applied: it’s the raw data, rounded of course. If I were Vermont, I’d stick with MCD-to-MCD flows as the best bet for controls. Adjust/factor any of the TAZ-to-TAZ flow data to MCD-to-MCD. Happy Ides of March, Chuck Purvis Hayward, California _______________________________________________ CTPP mailing list -- ctpp(a)listserv.transportation.org To unsubscribe send an email to ctpp-leave(a)listserv.transportation.org _______________________________________________ CTPP mailing list -- ctpp(a)listserv.transportation.org To unsubscribe send an email to ctpp-leave(a)listserv.transportation.org