I agree completely. We use tracts only (1) in thematic maps with
broad categories, or (2) for aggregation. This goes for all uses of
ACS data, not just CTPP.
At 07:50 PM 4/16/2009, you wrote:
Todd Graham makes all the right points. CTPP is
thin (and IMO not usable at any fine granularity such as CT, let alone TAZ).
On Wed, Apr 15, 2009 at 1:16 PM,
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1. RE: RE: Census Bureau Federal Register Notice on New
DataDisclosure Restrictions (Michael Moan)
2. remove (Brian Raimondo)
Date: Wed, 15 Apr 2009 14:42:30 -0400
From: "Michael Moan" <<mailto:MMoan@doa.ri.gov>MMoan@doa.ri.gov>
Subject: RE: [CTPP] RE: Census Bureau Federal Register Notice on New
Content-Type: text/plain; charset=US-ASCII
Yes this is too much and one of the reasons I opted out last time.
<mailto:JSabula@rideuta.com>JSabula@rideuta.com 4/15/2009 1:38 PM >>>
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.
Utah Transit Authority
[mailto:firstname.lastname@example.org] On Behalf Of Agnello, Paul
Sent: Wednesday, April 15, 2009 10:22 AM
To: Ed Christopher; Graham, Todd; Penny Weinberger;
Cc: Memmott, Jeff <RITA>;
Curling,Samuel F.; Weiner,Ed <OST>;
Rick L.; Fred(a)NARC.org
Subject: [CTPP] RE: Census Bureau Federal Register Notice on New
From a state planning perspective, I think it is
(whether it is due to new tighter disclosure rules or the
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. Virginia's share more than tripled in
cost from 2000 to 2010. I agree with the earlier point that if states
are paying for the special tabulations, there should not be these new
disclosure restrictions governing the release of the data. I am not
clear on why the disclosure restrictions are even an issue since I am
not aware of any past disclosure issues with the 2000 or prior CTPP and
mining CTPP data would not appear to be a particularly effective way for
someone to try to find out personal info. about someone else. If this is
such an issue, why was it not a problem in the past?
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
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
Virginia Department of Transportation
Transportation & Mobility Planning Division
1401 East Broad Street Telephone (804) 786-2531
Richmond, Virginia 23219-2000 Fax (804) 225-4785
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From: Ed Christopher [mailto:email@example.com]
Sent: Wednesday, April 15, 2009 12:07 AM
To: Graham, Todd; Penny Weinberger
Cc: Murakami, Elaine; Agnello, Paul;
<mailto:firstname.lastname@example.org>email@example.com; Pickard, Andy, P.E.;
Jeff <RITA>; <mailto:firstname.lastname@example.org>email@example.com;
Weiner, Ed <OST>;
Subject: Re: Census Bureau Federal Register Notice on New Data
Todd--You should have posted to the full CTPP listserve. You make all
good points that people need to think about. One point of
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
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
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
Re: protecting the individual confidentiality of respondents. True,
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%
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
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
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
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,
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
-- Todd Graham
390 Robert Street North
Saint Paul, MN 55101
19900 Governors Dr
Olympia Fields, IL 60461
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ctpp-news mailing list
Date: Wed, 15 Apr 2009 15:41:36 -0400
From: "Brian Raimondo"
Subject: [CTPP] remove
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Please remove me from all the mailing lists.