31 May
2007
31 May
'07
4:02 p.m.
The first CTPP product from ACS we hope will be a 3-year summary (ACS
records from 2005 thru 2007). Clearly, people want a flow tabulation.
The 3-year tabulations are limited to geographic units of 20,000 persons
or more. We currently don't have a DIFFERENT population threshold for
FLOW tabulation based on 3-years of ACS records, but the CTPP Technical
Group has been assuming we would want:
County -to- County
Place -to-Place
Perhaps: County - to-Place
Place -to- County
Using the same 20,000 population threshold. AND THEN, AFTER WORKPLACE
ALLOCATION IS COMPLETE, TO HAVE PUMA-TO-PUMA where PUMA of work is not
limited to COUNTY, but is a "real" sub-county PUMA where available.
The geography for tabulation for this first 3-yr ACS would be restricted
to Census 2000 geography, so we can't include "new" PUMAs defined for
Census 2010 until probably 2011 or 2012.
http://www.bea.gov/scb/pdf/2004/11November/1104Econ-Areas.pdf by
Kenneth P. Johnson and John R. Kort
There are 179 BEA Economic areas which are county-based. There are 344
component economic areas, which are merged into the 179 Economic Areas.
I am wondering if we might use either BEAs or CEAs to calculate either
quartile or quintiles to tabulate income for CTPP. I like the CEAs
because, for example in the Seattle area, the CEAs separates out the
western counties that are fairly rural in nature from the main urban
core counties.
Therefore the Part 3 tables might look like this:
TABLES for FLOW:
Table 1. Total workers
Table 2. Workers in group quarters (no characteristics)
Table 3. Means of Transportation to Work (7) (all workers)
Table 4 Income quartiles (4) or Income quintiles (5) (workers in
households) (Then, we would have to include a CHART documenting the
quartile or quintile values for each of the Economic areas, since they
would not be the same # from one area to the next).
Therefore, no crosstab of means of transportation by income in the FLOW
tabulation. Nandu has been researching using IPF routines to synthesize
a crosstab of means of transportation by income for FLOW for "base"
TAZs.
Because the BEA Economic Areas are large enough, there should be
sufficient ACS samples from which to calculate quartiles or quintiles
for household income. If there are approx 2 million completed h.u. ACS
forms each year, there would be about 11,000 households per BEA economic
area (BEA), or 5,800 households per Component economic area (CEA). This
avoids the problem of "too many" income categories that result from
trying to address variability between places like San Francisco-Oakland
and Nashville. Therefore a 3-year accumulated ACS would give us
approx 33,000 households for BEA, and 17,400 households for CEA. So,
the first step would need to be to calculate the values for each BEA or
CEA, and then tabulate the ACS records based on those values.
One of the biggest problems with this approach is that it would be up to
the data user to KNOW which BEA or CEA area was used. And, we would
have to check to see if there are MPOs that cross BEA or CEA boundaries.
Let me know what you think about this idea.
Elaine Murakami
FHWA Office of Planning
206-220-4460