25 Feb
2009
25 Feb
'09
2:46 p.m.
While ACS does not have county-to-county flows specifically, the PUMS dataset does have
flow data. Many counties are large enough to meet or exceed the 100,000 threshold for a
PUMA, so some county-to-county flow data can be obtained. Thurston County sits at the
south end of the Seattle-Tacoma metro area, and I am able to use PUMS data for flows
between Thurston (population 250,000) and Pierce (800,000) and King (1,900,000) counties,
but not to the small rural counties to our west and south. So for us, the PUMS data
provides half a loaf. Maybe it will provide a whole loaf for some of you. Also, you must
conscientiously calculate margins of error so that you can be sure that the figures are
statistically significant. Especially with the annual data, margins of error can exceed
annual changes in reported flow amounts because the sample size is only 1%.
Pete Swensson, Senior Planner
Thurston Regional Planning Council
2424 Heritage Ct. SW
Olympia, WA 98502
(360) 741-2530 (direct line)
(360) 956-7575 (main desk)
(360) 956-7815 (fax)
swenssp(a)trpc.org
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-----Original Message-----
From: ctpp-news-bounces(a)chrispy.net [mailto:ctpp-news-bounces@chrispy.net] On Behalf Of Ed
Christopher
Sent: Wednesday, February 25, 2009 12:01 PM
To: ctpp-news maillist
Subject: [CTPP] ACS Commuting Data
I received this in my email but thought answering it would be relevant to the larger CTPP
group.
-----------
Garth wrote:
Elaine/Ed:
Has there been any county-to-county commuting data yet from the American Community Survey?
Unless I've missed it somewhere, I don't think there has been since not all
counties are available yet. Will county-to-county commuting flow data be available in the
next ACS/CTPP multi-year product? If so, are we still looking at 2011 for the release
of such data? I'd appreciate any clarifications/references you could provide.
Thanks,
Garth
-----------
The short answer is that there has not been any county-to-county commuting data yet and
the Census Bureau has been mute on the question of ever producing any as part of their
standard tabulation program.
Using "Magic 8 ball" speak one could speculate that "it is doubtful"
if they ever would.
However, all is not lost! The transportation community has been very vocal that "We
NEED Flows." As such the AASHTO CTPP Oversight Board is positioning itself to
request a set of tables which will include flows.
The request is set to get to the Census Bureau by April 1, 2009.
Currently, a task force is working on the tables and ironing out a few bumps in terms of
what tables to ask for and the modal collapsing schema that might pass disclosure rules.
The task forces is very close to done. (The December newsletter talks about the
disclosure hurdles http://www.trbcensus.com/newsltr/sr1208.pdf). Once we get the tables
pinned down in the next few weeks we will certainly be circulating them to our large
community.
In terms of tables, the request will go to the Census Bureau by April 1st and then the
Disclosure Review Board will have to rule and then cost estimates will need to firmed up
and contracts written. If all goes well, the tables would use the 2006, 2007 and 2008 ACS
data with possible receipt of some data by 2010/2011. We have been told that the actual
production of the tables can go quite quickly once we get over all the stuff at the front
end. Right now, a lot has to fall in place but the message has been heard that, FLOW DATA
is MUST.
Right now the only reference is the letter that was sent from the Oversight Board on
February 9th stating that we are working on a 3-year ACS data table request. I have
attached it. Stay tuned.....
Ed Christopher
708-283-3534 (V)
708-574-8131 (cell)
FHWA RC-TST-PLN
19900 Governors Dr
Olympia Fields, IL 60461
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