Dear Everyone:
Today, the Census Bureau
issued this Federal Register notice. The 5-year ACS is the first
ACS product for small area geography, e.g. census tracts and block
groups. I have extracted KEY POINTS that will GREATLY IMPACT
data availability for transportation tables and result in a lot of DATA
SUPPRESSION at the tract and block group level. As this FR was just
issued today, we have not had a chance to estimate the amount of suppression
that would occur given these proposed conditions.
We are currently working on
profile sheets using the 2005-2007 ACS (3-year data) that was released in
December 2008. We are finding many tables to be suppressed.
So, even with the population threshold of 20,000 for the 3-year ACS data, there
is considerable suppression on the current ACS standard table production, at
least those tables of key interest to transportation planners.
As most of you know, the
first CTPP using ACS is a planned 3-year accumulation from ACS 2006-2008.
The table list will be re-submitted by AASHTO to the Census Bureau in a few
weeks.
The next CTPP product is
envisioned as a 5-year accumulation from ACS 2006-2010. Because of the
many rules the CB has established to protect individual confidentiality not
just for the ACS Standard tables, but also for custom tabulations like the
CTPP, we believe that the 5-year CTPP for small area tabulation (e.g. TAZs)
will need to rely on synthetic data generated inside the CB using the ACS
microdata records.
_________________________________________________________
*Federal Register Notice:
The 5-Year ACS Data Products Release Plan
Today the U.S Census Bureau
published its data release plan for the ACS 5-year data products in the Federal
Register (E9-4803). Beginning in late 2010, the Census Bureau plans to
introduce 5-year data products covering the January 2005 through December 2009
data collection period. The release of the 5-year estimates will achieve
the goal of the ACS to provide small area data similar to the long-form sample
data published after Census 2000.
The Census Bureau is
proposing to modify its current line of data products to accommodate the 5-year
estimates and is requesting comments from current and potential users of ACS
data products to help guide this modification.
We invite you to review the
5-Year ACS Data Release Plan and provide your response to the contact listed in
the Federal Register notice. Please follow this link to the Federal Register
notice (PDF files) posted in the Highlights section on the ACS Main page:
http://www.census.gov/acs/www/
Comments are due to the
contact listed in the Federal Register notice by April 20, 2009
From the Census
Bureau’s pdf document:
2. Detailed tables with
more than 100 cells cannot be released at the block group level.
5. For the Selected
Population Profiles, there must be at least 50 unweighted sample cases
over the 5-year period in
the universe (specific population subgroup) in a given
geographic area for the
profile to be released.
6. For workplace tables,
there must be at least 50 unweighted or 300 weighted workers in
sample over the 5-year
period in a given workplace for the table to be released.
7. For the residence and
workplace tables where means of transportation (mode) is crossed
with one or more other
variables, there must be at least three unweighted workers in
sample for each
transportation mode in a given place for the table to be released.
Otherwise the data must
be collapsed or suppressed and complementary suppression must
be applied. There is no threshold on univariate tables.
Elaine Murakami
FHWA Office of Planning
elaine.murakami@dot.gov
Note: please update my contact information. My previous email
address will likely expire on March 11.
206-220-4460