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
<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(a)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(a)cityofmadison.comwww.MadisonAreaMPO.org <http://www.madisonareampo.org/>
Change is "part and parcel" of why we do all of this analysis and data
collection. To some degree it is to understand today (not easy given the
lags in data collection vs. reporting timeframes) but it is more important
for most planning-related work to understand how changes are likely to play
out. Understanding trends and dynamics is why we do what we do- at least
those of us in the forecasting world.
Some places use longitudinal panel surveys to inform forecasting- a very
useful albeit expensive approach to develop an understanding of forecasting
likely changes. Digging around in the multi-year data sounds like an
excellent and perhaps low-cost way to add even more insight to understanding
the dynamics of change- even if you can't get a statistically valid measure
for every variable/geography in there.
Chiming in with Ken C., that too should somehow fit into the overall
research plan if we're going to maximize our "return on investment" on the
multi-year survey data sets.
I guess I'm up to a quarter's worth of thoughts now (or at least a nickel).
W
-----Original Message-----
From: ctpp-news-bounces(a)chrispy.net [mailto:ctpp-news-bounces(a)chrispy.net]
On Behalf Of ctpp-news-request(a)chrispy.net
Sent: Tuesday, February 01, 2011 4:26 PM
To: ctpp-news(a)chrispy.net
Subject: ctpp-news Digest, Vol 84, Issue 5
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Today's Topics:
1. Re: 2000 and 2006-08 work trip comparison question.
(Ed Christopher)
2. RE: 2000 and 2006-08 work trip comparison question.
(Planning Department)
----------------------------------------------------------------------
Message: 1
Date: Tue, 01 Feb 2011 14:53:19 -0600
From: Ed Christopher <edc(a)berwyned.com>
Subject: Re: [CTPP] 2000 and 2006-08 work trip comparison question.
To: ctpp-news(a)chrispy.net
Message-ID: <4D4872BF.7040902(a)berwyned.com>
Content-Type: text/plain; charset=ISO-8859-1; format=flowed
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:
> 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 naove 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(a)marc.org<mailto:flenk(a)marc.org>
> 816.701.8237
>
> From: ctpp-news-bounces(a)chrispy.net [mailto:ctpp-news-bounces(a)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(a)mrcog-nm.gov<mailto:tgaudette(a)mrcog-nm.gov>
>
>
>
>
> This email and any files transmitted with it are confidential and intended
solely for the use of the individual or entity to which they are addressed.
If you have received this email in error please notify the system manager.
This message contains confidential information and is intended only for the
individual named. If you are not the named addressee you should not
disseminate, distribute or copy this e-mail.
>
>
> From: ctpp-news-bounces(a)chrispy.net [mailto:ctpp-news-bounces(a)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(a)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(a)cityofmadison.com<mailto:dseidensticker(a)cityofmadison.com>
> www.MadisonAreaMPO.org<http://www.madisonareampo.org/>
>
>
>
> ------------------------------------------------------------------------
>
> _______________________________________________
> 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
4749 Lincoln Mall Drive, Suite 600
Matteson, IL 60443
------------------------------
Message: 2
Date: Tue, 1 Feb 2011 15:05:03 -0500
From: Planning Department <PlanningDepartment(a)countyofberks.com>
Subject: RE: [CTPP] 2000 and 2006-08 work trip comparison question.
To: "ctpp-news(a)chrispy.net" <ctpp-news(a)chrispy.net>
Message-ID:
<D465CB8E9BCA0249BB15FC9E59276F33A658EDC922(a)MSCLS001.countyofberks.com>
Content-Type: text/plain; charset="iso-8859-1"
Frank:
I agree wholeheartedly with your concerns. One particular issue that we, as
data 'superusers' need to remember, is every federal, state, and nonprofit
application for aid, grants, loans, etc. will still ask for the same
information for a set time. The vast majority of people are still--and will
be for a long time--used to using data derived from a "point in time
snapshot". Getting us used to working with 'trends' and 'characteristics'
has been difficult enough. We now have to pass that knowledge and practice
onto those to whom we give that data, whether it be the press, elected
officials, nonprofit agencies, students, or the general public.
This goes beyond our transportation uses, but at the same time has a
significant impact on our transportation uses of these data.
Michael D. Golembiewski
Transportation Modeler
BERKS COUNTY PLANNING COMMISSION
633 Court Street FL 14
Reading, PA 19601
Ph: 610 478-6300 ext 6304
Fax: 610 478-6316
e-mail:
mgolembiewski(a)countyofberks.com<mailto:mgolembiewski(a)countyofberks.com>
Web: http://www.co.berks.pa.us/dept/planning
Note: The comments on and attachment to this e-mail are intended only for
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________________________________
From: ctpp-news-bounces(a)chrispy.net [mailto:ctpp-news-bounces(a)chrispy.net]
On Behalf Of Frank Lenk
Sent: Tuesday, February 01, 2011 2:30 PM
To: ctpp-news(a)chrispy.net
Subject: RE: [CTPP] 2000 and 2006-08 work trip comparison question.
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 naove 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(a)marc.org<mailto:flenk(a)marc.org>
816.701.8237
From: ctpp-news-bounces(a)chrispy.net [mailto:ctpp-news-bounces(a)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(a)mrcog-nm.gov<mailto:tgaudette(a)mrcog-nm.gov>
This email and any files transmitted with it are confidential and intended
solely for the use of the individual or entity to which they are addressed.
If you have received this email in error please notify the system manager.
This message contains confidential information and is intended only for the
individual named. If you are not the named addressee you should not
disseminate, distribute or copy this e-mail.
From: ctpp-news-bounces(a)chrispy.net [mailto:ctpp-news-bounces(a)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(a)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(a)cityofmadison.com<mailto:dseidensticker(a)cityofmadison.com>
www.MadisonAreaMPO.org<http://www.madisonareampo.org/>
Penny:
I would chime in that my experience suggests all data and findings should be
compared as the differences, whether due to methodology, underlying
assumptions, or actual observed change can add great insight and "point the
way" towards the answers desired.
Such comparisons often highlight differences and should help analysts start
to comprehend the weaknesses and strengths of data upon which they're
building assumptions. It doesn't make one set of data more "right" than
another, just a different perspective. I always ask "what does the
comparison tell me?" Does the comparison yield differences and similarities
I expect? Are the findings consistent with other "common wisdom"? If no,
why not?
For example, take a few very different data sources: the CTPP, ACS, NHTS,
QCEW, IRS, D&B and InfoUSA. Each include very different ways of estimating
employment. All are incomplete but paint part of the picture. Taken
together, I can see patterns and weigh the relative strength of each one's
methodology to meeting a specific need.
How are part-time jobs treated? How about sole proprietors? How about
workers with more than one job? Workers that work one day/week or month?
1099 workers? Volunteers? Seasonal workers? Military? Are there things
missing, discounted or even double-counted in one vs. the other?
Understanding Standard Error terms is one thing, understanding utility and
suitability is quite another.
Even trying to answer a simple question such as "how many jobs/workers are
there at a given moment in time" doesn't have a simple answer or at least
there isn't one dataset that will answer it depending on the definition of
job/worker I'm looking for to meet a specific need.
One "comparison" I was looking at in the 2000 vs. 2009 3 year data is a
simple "relative order" of destination county in one dataset vs. the other
(row-wise relative ranking). Comparing the 2009 3 Year data (off your
wonderful website) vs. 2000 CTPP would seem to have merit. See below:
Are the changes consistent with what is known about the economic and
development change in the area? Observed traffic flows (yet more data) and
changes in the flows over time? What's missing or considered incompletely
in each dataset? Do the differences in the dataset suggest I need to use
them to inform decision-making differently.
All fair and good comparisons (and questions) that help provide me some
level of insight both into data differences and change. For a "real-world"
comparison of two different dataset that has made a difference in
understanding, think about the release and subsequent re-release of the NHTS
based on comparisons made between its findings and the NTD for US transit
ridership. The comparison highlighted additional considerations that would
need to be included in the weighting process for NHTS. Without the
comparison, the suitability of NHTS for certain transit analyses would be in
question.
The more comparisons we make and questions we ask the better the data gets
and the better the understanding of its limitations. Of course, if we
blindly use any data, caveat emptor.
My 2 cents.
W
-----Original Message-----
From: ctpp-news-bounces(a)chrispy.net [mailto:ctpp-news-bounces(a)chrispy.net]
On Behalf Of ctpp-news-request(a)chrispy.net
Sent: Monday, January 31, 2011 11:06 AM
To: ctpp-news(a)chrispy.net
Subject: ctpp-news Digest, Vol 83, Issue 32
Send ctpp-news mailing list submissions to
ctpp-news(a)chrispy.net
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When replying, please edit your Subject line so it is more specific
than "Re: Contents of ctpp-news digest..."
Today's Topics:
1. RE: 2000 and 2006-08 work trip comparison question.
(Weinberger, Penelope)
2. RE: 2000 and 2006-08 work trip comparison question.
(Kendra Watkins)
----------------------------------------------------------------------
Message: 1
Date: Mon, 31 Jan 2011 10:41:28 -0500
From: "Weinberger, Penelope" <pweinberger(a)aashto.org>
Subject: RE: [CTPP] 2000 and 2006-08 work trip comparison question.
To: <ctpp-news(a)chrispy.net>
Message-ID:
<94A99461953E3341B89642B00D5C0B7D0705A4B4(a)AASHTO-MAIL.aashto.local>
Content-Type: text/plain; charset="us-ascii"
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
<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(a)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(a)cityofmadison.comwww.MadisonAreaMPO.org <http://www.madisonareampo.org/>
For those folks who are interested in what others of us are doing with
ACS data here are some links to what the Baltimore MPO has been up to.
They were sent to me by friend Charles Baber of Baltimore Metro Council.
Thanks Charles
http://www.baltometro.org/maps-and-data/american-community-survey
---------------------
In December 2010, the Census Bureau released ACS data from 2005-2009 for
small geographic areas. Using this data, BMC has produced a series of
thematic maps that provide snapshots of the entire Baltimore region, as
well as of each jurisdiction. These include:
* Population Density (region)
* Race and Hispanic Heritage (region)
* Median Household Income (by jurisdiction)
* Poverty (by jurisdiction)
* Unemployment (by jurisdiction)
* Homes Where Mortgage Is More Than 30% of Income (by jurisdiction)
* Rental Units Where Rent Is More Than 30% of Income (by jurisdiction)
* Workers Who Take Public Transportation to Work (by jurisdiction)
In addition, BMC has created an interactive online map where data can be
viewed at the Regional Planning District (RPD) level. The RPDs follow
census boundaries and contain one or more census tracts. There are 94
RPDs in the Baltimore region. To see data for a particular RPD, simply
click on that location and ACS 2005-2009 data will appear.
http://www.baltometro.org/
--
Ed Christopher
708-283-3534 (V)
708-574-8131 (cell)
FHWA RC-TST-PLN
4749 Lincoln Mall Drive, Suite 600
Matteson, IL 60443
