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.
Patty Becker
At 07:50 PM 4/16/2009, you wrote:
Todd Graham makes all the right
points. CTPP is statistically very thin (and IMO not usable at any
fine granularity such as CT, let alone TAZ).
Keith
On Wed, Apr 15, 2009 at 1:16 PM,
<
ctpp-news-request@chrispy.net> wrote:
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- Today's Topics:
- 1. RE: RE: Census Bureau Federal Register Notice on New
- DataDisclosure Restrictions (Michael
Moan)
- 2. remove (Brian Raimondo)
-
----------------------------------------------------------------------
- Message: 1
- Date: Wed, 15 Apr 2009 14:42:30 -0400
- From: "Michael Moan"
<MMoan@doa.ri.gov>
- Subject: RE: [CTPP] RE: Census Bureau Federal Register Notice on
New
- DataDisclosure Restrictions
- To:
<ctpp-news@chrispy.net
>
- Message-ID:
<s9e5f27d.037@ri.gov>
- Content-Type: text/plain; charset=US-ASCII
- Yes this is too much and one of the reasons I opted out last
time.
- >>>
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.
- Julianne Sabula
- Utah Transit Authority
- -----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. 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
- 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
- Virginia Department of Transportation
- Transportation & Mobility Planning Division
- 1401 East Broad Street Telephone (804) 786-2531
- Richmond, Virginia 23219-2000 Fax (804) 225-4785
- 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,
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- 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
- > 390 Robert Street North
- > Saint Paul, MN 55101
- >
- > 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
- 19900 Governors Dr
- Olympia Fields, IL 60461
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- ------------------------------
- Message: 2
- Date: Wed, 15 Apr 2009 15:41:36 -0400
- From: "Brian Raimondo"
<braimondo@swfrpc.org>
- Subject: [CTPP] remove
- To:
<ctpp-news@chrispy.net
>
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