This is why five year average data do, and will, need to be used with
caution. No one would want to average 2003-7 in New Orleans!
That's why it's good that we will have the 1 year data sets for places of
65,000 or more population and 3 year data sets for places of 20,000 or
more. Ten years from now we can write articles analyzing the good
and bad of 5 year accumulations of data. For now, we just have to
be careful.
I completely agree that sampling error and absence of group quarters both
raise their ugly heads when working with ACS data. But including
group quarters, if the bureau gets to do it, won't solve the whole
problem, because there is likely to be a lot of sampling error
there.
Patty Becker
At 04:50 PM 09/13/2005, you wrote:
I think there is a major problem
in the ACS survey data for 2004 because of not including group
quarters. Princeton University is in Mercer County, and a good part
of its student population is housed in dorms or eating groups
(fraternities), which are group quarters. Something like 40% of the
work trips in Princeton Boro are walk to work, probably mostly univeristy
related jobs, and students employed within the Boro. The ACS
leaving out group quarters may explain part of this. I also have a
problem with aggregating 5 years of data and calling it a 5 year
average. NJT opened a 33 mile Light Rail line in early 2004,
connecting Trenton to Camden. I noticed in the Burlington County
data a big jump in "railroad" work trips, probably related to
this new rail line. How does a major change in transit service get
averaged with 3 other years when it is a permanent change. This
applies to any region where a major change in transit service gets
implemented. What about possible sh!
ifts in carpooling this year due to gas prices. A 5 year
average may not be worth much. I think Dr. Zakaria raises some real
issues here, especially with big error rates, and I think major changes
in transit service, gas prices etc. can skew things.
-----Original Message-----
From: ctpp-news-bounces@chrispy.net
[mailto:ctpp-news-bounces@chrispy.net]
On Behalf Of Thabet Zakaria
Sent: Tuesday, September 13, 2005 9:54 AM
To: ctpp-news@chrispy.net
Subject: [CTPP] 2004 ACS Data Release
2004 ACS Data Release by Thabet Zakaria dated September 12, 2005 is
resubmitted in PDF.
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Patricia C. (Patty)
Becker
248/354-6520
APB
Associates/SEMCC
FAX 248/354-6645
28300 Franklin
Road
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Southfield, MI
48034
pbecker@umich.edu