New subject: CB Federal Register Notice: ACS 5-year data products proposal

6 Mar 2009

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(a)dot.gov 

Note:  please update my contact information. My previous email address
will likely expire on March 11.

206-220-4460