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