[CTPP] With ACS make sure to Read the Small Print

[Ed Christopher]

Earlier this week I was part of an email chain where it was discovered 
that with the new 2008 ACS data which was just release there was a 
national change in workers from 2007 of about 4.8 million for a growth 
of about 3.4 percent. Of course this seemed odd given the year that we 
have been through.  I further learned that BLS was showing a loss of 
workers during the same time which prompted me to pass the issue over to 
Melissa Chiu our CTPP coordinator at the Census Bureau.  Here is what 
Melissa had to say.

Hi Ed,
I spoke with the subject matter branch chief and it turns out that the
Bureau recommends using caution when making labor force comparisons 
between data from 2008 or later and data from prior years (make sure to 
look at the footnote at the bottom of the labor force tables). This is 
because there was a question change starting in 2008 that results in 
more people responding that they worked last week. The question in use 
before 2008 missed many marginal workers. Essentially the data are 
better now and this also puts the ACS data more in line with the Current 
Population Survey (CPS)-based BLS data. In addition, as far as labor 
force estimates go, the BLS data are considered the official estimates, 
and many more questions are asked on the CPS regarding employment than 
on the ACS. So there may still be differences between CPS and ACS due to 
this and other issues.

There is more information on this question change in the research note:
http://www.census.gov/hhes/www/laborfor/researchnote092209.html

The note references the following 2006 content test report that resulted 
in the question change:
http://www.census.gov/acs/www/AdvMeth/content_test/P6a_Employment_Status.pdf

Finally, for other information on labor force data, please start here:
http://www.census.gov/hhes/www/laborfor/laborforce.html

I hope this helps. If you have further questions, please let me know and 
I will refer you to the appropriate person.

Thanks, Melissa

-- 
Ed Christopher
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