1 Feb
2011
1 Feb
'11
3:17 p.m.
If you see the point about the problem of
comparing overlapping 3 year ACS estimates, it
gets even worse with consecutive 5 year numbers,
in which 4 of the 5 years are the same data.
Personally, I think there's a strong argument for
releasing 5 year data only twice a decade, by
definition non-overlapping. We may get to that point in a couple of years.
Patty Becker
At 03:53 PM 2/1/2011, you wrote:
Frank-I totally agree and I would like to see
the statisticians get involved and think about
this. People are going to compare overlapping
periods and we have to get smart about how to deal with this.
As for why some say we should not compare
overlapping years the story goes like this. If
you have 2006 to 2008 data and 2007 to 2009 data
you would have two overlapping years. According
to the logic you would in fact only be comparing
the first year 2006 to the last year 2009 as the
middle two years would cancel themselves
out. While this sounds logical on the surface
there has to be a way to deal with overlapping
5-year periods or it doesn't make sense to have an ACS.
I am not sure if anyone would out right admit it
but is anyone designing performance measures or
other regional metrics calling for tracking
annual multi-year period estimates at tracts or places?
Frank Lenk wrote:
-------------------------------------------------------------------------------------------------
Patricia C. (Patty) Becker 248/354-6520
APB Associates/SEMCC FAX 248/354-6645
28300 Franklin Road Home 248/355-2428
Southfield, MI 48034 pbecker(a)umich.edu
I would also be interested in a more detailed
explanation of why we should not compare
overlapping period estimates. From a practical
standpoint, people are going to do it anyway,
especially the press. What do we need to know
- other than the inherent issues of what is a
statistically significant vs. insignificant
change and the fact that ACS was designed to
examine characteristics of the population
rather than its level - to be able to correct
naïve interpretations of easily calculated
tract-level year-to-year differences in the
estimates of things like poverty rate,
unemployment rate, educational attainment
rates, etc.? What is a correct interpretation of these differences?
Frank
Frank Lenk
Director of Research Services
Mid-America Regional Council
600 Broadway, Suite 200
Kansas City, MO 64105
www.marc.org<http://www.marc.org>
816.474.4240
flenk@marc.org<mailto:flenk@marc.org>
816.701.8237
From: ctpp-news-bounces(a)chrispy.net
[mailto:ctpp-news-bounces@chrispy.net] On Behalf Of Kendra Watkins
Sent: Monday, January 31, 2011 10:05 AM
To: ctpp-news(a)chrispy.net
Subject: RE: [CTPP] 2000 and 2006-08 work trip comparison question.
This is interesting. I recall hearing this
guidance in the past. However on the Census
website on the ACS page it specifically states;
"Generally, you can compare American Community
Survey (ACS) 3-year and 5-year estimates with
Census 2000 data. There are differences in the
universe, question wording, residence rules,
reference periods, and the way in which the
data are tabulated which can impact comparability."
The qualifier in the second sentence addresses
the conflict (different methods, time periods
etc) but I can't find anywhere on the ACS pages
where the Census recommends we not compare ACS
to decennial Census. And when I search by
subject the Journey to Work topic states that I
can 'Compare' it to the 2000 Census.
It does specifically state not to compare
overlapping years on multiyear estimates.
Kendra Watkins
Senior Data Analyst
Mid-Region Council of Governments
809 Copper Ave. NW
Albuquerque, NM 87102
Phone: (505)724-3601
Fax: (505)247-1753
Email: kwatkins@mrcog-nm.gov<mailto:tgaudette@mrcog-nm.gov>
This email and any files transmitted with it
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From: ctpp-news-bounces(a)chrispy.net
[mailto:ctpp-news-bounces@chrispy.net] On Behalf Of Weinberger, Penelope
Sent: Monday, January 31, 2011 8:41 AM
To: ctpp-news(a)chrispy.net
Subject: RE: [CTPP] 2000 and 2006-08 work trip comparison question.
The CB does not recommend comparing an ACS
based data set to a CB Long Form based data
set. The 2000 data represent a point in time
estimate, the ACS data represent a period
estimate. Furthermore, the Census Bureau
recommends not comparing period estimates with overlapping years.
Penelope Weinberger
CTPP Program Manager
AASHTO
202-624-3556
http://ctpp.transportation.org/Pages/default.aspx
It's just as bad to not make a plan as to
blindly follow the one you already have.
From: ctpp-news-bounces(a)chrispy.net
[mailto:ctpp-news-bounces@chrispy.net] On Behalf Of Seidensticker, Dan
Sent: Friday, January 28, 2011 4:18 PM
To: (ctpp-news(a)chrispy.net)
Subject: [CTPP] 2000 and 2006-08 work trip comparison question.
We downloaded the2006-2008 ACS county-to-county
worker flow for Dane County, Wisconsin from
http://ctpp.transportation.org/Pages/3yrdas.aspx.
The question we now have...can that data be
compared to the county-to-county 2000 CTPP work
trips to determine any statistically
significant increase/decrease? If so, how
would one calculate the margin of error?
Dan Seidensticker
GIS Specialist
Madison Area Transportation Planning Board:
A Metropolitan Planning Organization (MPO)
City of Madison Planning Unit
121 S. Pinckney Street, Suite 400
Madison, WI 53703
Voice: 608-266-9119
Fax: 608-261-9967
Email:
dseidensticker@cityofmadison.com<mailto:dseidensticker@cityofmadison.com>
www.MadisonAreaMPO.org<http://www.madisonareampo.org/>
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