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

[Alan Pisarski]

Nate et al: they have told us in the past that the number of question and
the probing that goes on is way more than the ACS/decennial could absorb.  I
did a paper on this as I recall last time -- maybe in CIAIII. My main
thought is at least they owe us a side by side discussion of the numbers
from the three sources and a discussion of the likely differences within
groups.  My note to others on this is just below:

This (the difference in results) suggests that the disparity is because it
was weak last time. It further indicates that the growth levels would occur
in those areas of marginal workers and therefore perturb the modal shares
trend between years, etc.  There are other oddities that this would explain
-- or confound with the actual trend.  It would be very helpful if they
provided some tabular reference points -- such as mode usage by income class
or occupation and auto ownership by race, or income, etc.   

AEP   

Alan E. Pisarski
6501 Waterway Drive 
Falls Church Va. 22044
703 941-4257
alanpisarski at alanpisarski.com

-----Original Message-----
From: ctpp-news-bounces at chrispy.net [mailto:ctpp-news-bounces at chrispy.net]
On Behalf Of Nathan Erlbaum
Sent: Thursday, October 01, 2009 8:24 AM
To: ctpp-news at chrispy.net
Subject: Re: [CTPP] With ACS make sure to Read the Small Print

a logical person would then ask why aren't the questions that BLS or CPS
uses part of the acs?  would this increase the level of confidence and
reliability of these data?

>>> edc at berwyned.com 9/30/2009 7:23 PM >>>
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
708-283-3534 (V)
708-574-8131 (cell)

FHWA RC-TST-PLN
4749 Lincoln Mall Drive, Suite 600
Matteson, IL  60443

_______________________________________________
ctpp-news mailing list
ctpp-news at chrispy.net 
http://www.chrispy.net/mailman/listinfo/ctpp-news 


_______________________________________________
ctpp-news mailing list
ctpp-news at chrispy.net
http://www.chrispy.net/mailman/listinfo/ctpp-news