31 May
2007
31 May
'07
5:46 p.m.
Elaine, thanks for raising this. You are actually hitting on a much
broader topic that we need to begin to pin down. What will a three-year
CTPP data product look like? What will the Disclosure Review Board (DRB)
let us have? Unfortunately neither of these are simple to answer but
before we can begin any discussions with the DRB, we need to have the
data product in focus. On that note and more relevant to your post I
have a coupla thoughts.
1. I would think that states and those working on more longer distance
models would find some type of income flow data usable, especially at
the CEA level. I am not sure how usable it would be within a region.
Hopefully others will weigh in.
2. Regarding the list of 3-year flow tables I would suggest adding in
and inserting "Workers in Households (no characteristics)" as table 2
followed by GQ, etc. I know one could get workers in households by
subtracting one table from another (total from GQ) but that just begins
to add a layer of complexity.
3. I know we talked about this with the DRB but I have to keep reminding
myself that they have already said that we could get the same two Part 3
tables that we got with CTPP 2000 without any thresholds applied. Do
you think that same exemption would apply to just the flows of either
household workers or GQ workers without any other characteristics? Even
with the big geography (20,000 pop zones) we might have some suppression
impacts given the smaller sample associated with a three year product
especially because we are talking about unweighted records.
4. I like your idea of the mixed geography, e.g. county to place and
place to county. Maybe this could lead to getting people to think about
mixed TAZs in the future--a set of residence zones and a different set
of workplace zones.
"Murakami, Elaine" wrote:
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 dont 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 cant 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
---------------------------------------------------------------
_______________________________________________
ctpp-news mailing list
ctpp-news(a)chrispy.net
http://www.chrispy.net/mailman/listinfo/ctpp-news
--
Ed Christopher
708-283-3534 (V)
708-574-8131 (cell)
FHWA RC-TST-PLN
19900 Governors Dr
Olympia Fields, IL 60461