Friends of the Census:
This group would work much more efficiently if it had a
normal internet forum structure.
A forum isn’t very hard to establish and would allow
us to discuss the various issues without having to send emails to everybody all
the time.
-----Original Message-----
From: ctpp-news-bounces@chrispy.net [mailto:ctpp-news-bounces@chrispy.net] On
Behalf Of Sabula,Julianne Ruth (Engineering-Const Planner II)
Sent: Wednesday, April 15, 2009 10:38 AM
To: ctpp-news@chrispy.net
Subject: RE: [CTPP] RE: Census Bureau Federal Register Notice on
NewDataDisclosure Restrictions
Is there a way to reply just to the person you are conversing with? I
would rather access these messages on the discussion board if I'm interested
than empty my inbox once an hour.
Julianne Sabula
-----Original Message-----
From: ctpp-news-bounces@chrispy.net
[mailto:ctpp-news-bounces@chrispy.net] On Behalf Of Agnello, Paul
Sent: Wednesday, April 15, 2009 10:22 AM
To: Ed Christopher; Graham, Todd; Penny Weinberger;
ctpp-news@chrispy.net
Cc: Memmott, Jeff <RITA>; kcooper@dot.state.nv.us;
amy.thomas@ky.gov; robbins@wsdot.wa.gov; Murakami,Elaine;
ayalew.adamu@dot.ca.gov; sandy.beaupre@dot.state.wi.us;
willimasjs@dot.state.al.us; bobbi.retzlaff@dot.state.wi.us; dhardy@ampo.org;
nerlbaum@dot.state.ny.us; donna.weaver@po.state.ct.us; pleasantmd@scdot.org;
huiwei.shen@dot.state.fl.us; kmiller@njtpa.org; rdenbow@ampo.org;
Ron.fields@arkansashighways.com; jonette.kreideweis@dot.state.mn.us;
nsrinivasan@nas.edu; phil.mescher@dot.state.ia.us; Curling,Samuel F.; Weiner,Ed
<OST>; Pickard, Andy,P.E.; virginia.porta@arkansashighways.com;
Tambellini, Rick L.; Fred@NARC.org
Subject: [CTPP] RE: Census Bureau Federal Register Notice on New
DataDisclosure Restrictions
>From a state planning perspective, I think it is very disappointing
(whether it is due to new tighter disclosure rules or the statistical
reliability issue) that it appears that states and MPOs will not have the same
quality of CTPP data available in 2010 as in 2000 and previous census cycles.
Particularly since states are paying considerably more for the next CTPP than
for 2000.
While it may be too late to fix the problems associated with data
quality/content for the next CTPP, I'm wondering if there are ways that the ACS
sample could be increased with additional federal and/or state support in the
future so that this statistical reliability issue could be addressed, perhaps
in a process similar to the way NHTS is done, or perhaps CTPP data needs to
come from a different source long term if the ACS data is not reliable enough
to meet state and metropolitan planning needs.
Decision makers increasingly want to see more robust technical tools
and analysis which to support planning analysis which requires more detailed
data at the small area from sources such as ACS, CTPP, NHTS, etc., and major
conferences, e.g., TRB, and federal agencies have supported better data for
transportation planning for years. Therefore, from a state perspective, the
Census Bureau's proposed policy change run counter, not only to prevailing
trends, but to the policies from other federal transportation agencies.
-------------------------------------------
Paul T. Agnello
Travel Demand Modeling Manager
Transportation & Mobility Planning Division
1401 East Broad Street Telephone (804) 786-2531
E-mail: mailto:paul.agnello@VDOT.Virginia.gov
Website: http://www.virginiadot.org/
* CONFIDENTIALITY/PRIVACY NOTICE - The documents included in this
transmission may contain information that is confidential and/or legally
privileged. If you are not the intended recipient, or the employee or
agent responsible for delivering the information to the intended recipient, you
are hereby notified that any disclosure, copying, distribution, or action taken
in reliance on the contents of these documents is strictly prohibited. If
you have received this document in error, please notify the sender immediately
to arrange for return or destruction of these documents.
-----Original Message-----
From: Ed Christopher [mailto:edc@berwyned.com]
Sent: Wednesday, April 15, 2009 12:07 AM
To: Graham, Todd; Penny Weinberger
Cc: Murakami, Elaine; Agnello, Paul; banningag@michigan.gov;
sandy.beaupre@dot.state.wi.us; kcooper@dot.state.nv.us;
jonette.kreideweis@dot.state.mn.us; phil.mescher@dot.state.ia.us;
ayalew.adamu@dot.ca.gov; pleasantmd@scdot.org; virginia.porta@arkansashighways.com;
bobbi.retzlaff@dot.state.wi.us; robbins@wsdot.wa.gov;
huiwei.shen@dot.state.fl.us; amy.thomas@ky.gov; donna.weaver@po.state.ct.us;
willimasjs@dot.state.al.us; sharon.ju@h-gac.com; kmiller@njtpa.org; Pickard,
Andy, P.E.; creschovsky@mwcog.org; grousseau@atlantaregional.com;
Fred@NARC.org; rdenbow@ampo.org; dhardy@ampo.org; rmccready@aashto.org;
Memmott, Jeff <RITA>; nsrinivasan@nas.edu; Weiner, Ed <OST>;
Ron.fields@arkansashighways.com; nerlbaum@dot.state.ny.us
Subject: Re: Census Bureau Federal Register Notice on New Data
Disclosure Restrictions
Todd--You should have posted to the full CTPP listserve. You make all
good points that people need to think about. One point of
clarification
is that the AASHTO CTPP Oversight Board has sent a new proposal of
tables over to the CB for 3-year data and in fact the mode to work
questions are rolled up. I believe the largest roll-up is 3 modes:
auto, other and total. I took on the task of posting the new tables to
the Listserve but haven't done so yet. The tables are still fresh off
the press and I will not be able to get to it till Thursday.
One point that is missed in all of this is that with the 3-year data we
are talking about a zone system with 20,000 people per zone. That is
the size of 7 or so tracts. Pretty big when you are talking about
planning within a region. Even though you are right about the
statistical quality of the data the CB is not telling us there is a
statistical reason for suppressing the data. They are basing it solely
on disclosure requirements. Disclosure requirements and arguments that
can not be proven. Another point that is missed is that the old long
form data suffered from the same relative thinness at the tract, block
group and TAZ level. At those levels of geography many of the same
tables that are not passing the disclosure rules now would not have
passed then. Yes, the data today is a little thinner but that has
never
been the issue.
One last point is that CTPP has always been a special tabulation and if
you push the issue far enough logic should dictate that someone
purchasing a special tabulation should be allowed to buy whatever data
they want no matter how crappy it is. In 1980 the CB used to sell us
the data with a "caveat emptor" sticker on it.
Putting all the cards on the table does point to why synthetic data for
small area analysis is so important. Unfortunately there are not only
statistical issues of methodology to deal with but also practical
issues
of political acceptance within the community.
Graham, Todd wrote:
> State and MPO colleagues--
>
> Discussions about Census data disclosure have been making the
rounds. I wanted to share a few thoughts with the SCOP Census Data Work
Group...
>
> Re: protecting the individual confidentiality of respondents.
True, the Bureau itself is standing this up as their decision basis (it's a
legally powerful position). But I think the larger, latent, real concern among
the Bureau statisticians is statistical reliability.
>
> We know ACS sampling is thin (1 in 8 households surveyed, 60-65%
response rates?) and temporally spread out... And we know there will be large
numbers of individual data cells in the planned CTPP-from-ACS tabs where
estimates would be based on just 1 or 2 respondents. As a statistician, I
really don't like this. Resulting estimates are not robust. (There's great
uncertainty around whether the 1 or 2 survey respondents should represent 10-20
other people - or perhaps, by freak luck, the 1 or 2 persons are unique. There
is real probability of 1 or 2 respondents being *not* representative.) This is
particularly true in the most highly-detailed crosstabs. Hundreds of cells in
a table *will* result in many cells with small numbers.
>
> I know some members of SCOP have been drafting comments in
response to the Fed Register Notice. Some of these comments will make emphatic
proposals that we must have fully populated CTPP tables. I worry that this
line of reasoning won't have much traction at Census Bureau... And really, do
we believe that any numbers (regardless of statistical reliability) are better
than no numbers?
>
> As a statistician, I disagree - and I think there are creative
alternatives that are viable: (1) SCOP and Census Data Workgroup have discussed
data synthesis techniques to simulate or synthesize the desired details. Or
(2), a more conventional solution, more highly aggregated ("rolled
up") categorization in the CTPP-from-ACS tabs. What SCOP requested in
2007 looks a lot like CTPP 2000 -- even though we knew that ACS Survey sampling
is thinner than Census 2000.
>
> Sorry to bring this up, but here goes: AASHTO SCOP should revisit
the CTPP-from-ACS design, reopen it for discussion, go back to the drawing
board, and consider more highly aggregated ("rolled up")
categorizations in the CTPP-from-ACS tabs. Do we really need 10 (or 17)
categories of mode of travel (can we live with fewer)? Do we really need 25
categories of household income (can we live with fewer)? Do we really need
tabs with travel-start-time expressed in 15-minute intervals??
>
> I know there are sunken costs already. Still, my candid advice:
AASHTO SCOP and other funding partners in the CTPP need to take a deep
breath... and consider revising the special tabs requests. And Census Bureau
should cooperate and enable such a new plan.
>
> I understand that people are up-at-arms about this. (Census
Bureau, for their part, waited until 2008 to clearly signal that there would be
a tighter data disclosure regime than experienced in CTPP 2000...) But the
realpolitic is: Census Bureau statisticians have already decided this matter --
isn't the Fed Register notice just a formality? -- and from the standpoint of
good statistical science, their decision is right.
>
> -- Todd Graham
>
>
>
> ________________________
>
> Todd Graham
> Principal Forecaster
> Metropolitan Council
>
>
>
> phone 651/602-1322
> email todd.graham@metc.state.mn.us
> web www.metrocouncil.org
> www.metrocouncil.org/metroarea/stats.htm
> ________________________
>
>
>
--
Ed Christopher
708-283-3534 (V)
708-574-8131 (cell)
FHWA RC-TST-PLN
_______________________________________________
ctpp-news mailing list
ctpp-news@chrispy.net
http://www.chrispy.net/mailman/listinfo/ctpp-news
_______________________________________________
ctpp-news mailing list
ctpp-news@chrispy.net
http://www.chrispy.net/mailman/listinfo/ctpp-news