New subject: Geographic coverage, C2SS & ACS

8 Nov 2001

Why do we have tracts?
Yes, ed, your memory is correct about the Bureau "creating" census tracts,
but they relied on the recommendations of the local "Census Tract
Committees" of data users to provide the boundaries. This is still the
process for the decennial review of the tracts. (I worked on coordinating
this review in the Cincinnati CMSA for 1990 and 2000.)

But, we have census tracts mainly as geographically stable over time
statistical analytical areas. Municipalities, enumeration districts and
zip-codes, on the other hand, keep moving their boundaries. This is also the
reason that we can split census tracts in growing areas, but that they need
to nest to the same parent tract of the preceding census, and that the ID
tract numbers are changed with suffixes so that it is obvious that the areas
represented by the tract-split numbers aren't the same.

My experience with TAZ's, again with the Cincinnati MPO, is that you
wouldn't want to go there. We have just overhauled our tazs for 2000. Most
changes are splits, but some aren't. They don't match tracts. And many are
small enough to represent blocks in the CBD and major traffic generators
(shopping centers, employers) with little or no resident population to
disclose.

Census tracts are good.

Don Burrell, Senior Planner
Bicycle / Pedestrian Coordinator (formerly data person)
OKI Regional Council of Governments
801-B West Eighth St.  Suite 400
Cincinnati, OH 45203-1607
513-621-6300
513-621-9325 - fax
dburrell(a)oki.org <mailto:dburrell@oki.org> 
<A bicycle is an instrument for playing the road>

-----Original Message-----
From: ed christopher [mailto:edc@berwyned.com]
Sent: Thursday, November 08, 2001 4:37 PM
To: 'ctpp-news maillist'
Subject: Re: [CTPP] Re: Geographic coverage, C2SS & ACS

since patty raised the issue of tracts, i have often wondered why do we have
tracts?  why don't we
have a zonal system in urban areas that is created by the public data
users--something like TAZs.  in
many areas the TAZs are developed by a collection agencies with planning and
data responsibilities.
if memory serves me tracts were historically a creation of the census bureau
which is a data
collector.  TAZs are a product of regional planning organizations (which
happen to have
transportation responsibilities) which are data users.

Patty Becker wrote:

...
  Again, please feel free to post this to the list serve
if you wish.

 My clear understanding is that "small area" means tract.  I don't think
 anyone thinks the 60 month data will be good enough for block groups.

 If TAZs are tract equivalent, then the data should be as good as for
 tracts.  For heavy attractor TAZs which are split below tract level, the
 transportation community has to negotiate with the bureau for a special tab
...
  to deliver all TAZs.  The data should support the tab
 adequately,  Meanwhile, of course, someone is going to have to be
 responsible (MPO by MPO and state by state) for keeping the geocoding file
 up to date!

 No one knows whether these 60 month data are going to "feel right."  Only
 time will tell.  But in any event the CTPP users will have data equivalent
 to that for all users who use tracts.  Meanwhile, we still have all these
 hurdles in Congress, etc. etc.

 Patty Becker 
---
Ed Christopher
Metropolitan Specialist
Midwest Resource Center
Federal Highway Administration
19900 Governors Drive
Olympia Fields, Illinois  60461
708-283-3534 (V)
708-283-3501 (F)

RE: [CTPP] Re: Geographic coverage, C2SS & ACS