Hello Nick –  Your results are not unusual, and the CTPP listserv has had discussions about this in the past.  You can search the archives. http://www.chrispy.net/pipermail/ctpp-news/

You might want to read the article from Jan 2011 CTPP Status report by Nathan Erbaum (recently deceased).

http://www.fhwa.dot.gov/planning/census_issues/ctpp/status_report/sr0111.cfm

Also, Bruce Spear from Cambridge Systematics completed the NCHRP project mentioned in Nathan’s article. http://onlinepubs.trb.org/onlinepubs/nchrp/docs/NCHRP08-36(98)_FR.pdf

Bruce recently did a webinar for the Census Bureau and perhaps he can share the link to the recording (I assume it was recorded).

Finally, just last week, the LEHD project said they had added FEDERAL employment to their database, but I have not checked it yet to see if it makes sense.  Previous to this latest release, federal employment was NOT included.   I hope that several of you on the CTPP listserv will be taking the time to examine specific locations in your own area, e.g. major federal office buildings, major military installations, that have impacted the utility of the LEHD without requiring a lot of  edits and corrections. 

Also, as you know, the LEHD uses state QCEW and MWR reports, so it does not include self-employed.  Self-employed are estimated to be nearly 10 percent of workers, and more likely to work from home (which accounts for shorter commute trip length).   We have found in the past that school districts and other local governmental agencies may not distribute their workers to actual worksites and often report only one main address.  This occurred in Illinois, where all  state workers were  assigned to Springfield as their workplace location, but this was a long time ago, and may have been subsequently corrected.

There is a separate listserv for LEHD which you could try to post your query.   This page, which I have not updated in a long time, include a link to the listserv.

http://www.fhwa.dot.gov/planning/census_issues/lehd/

Elaine Murakami

FHWA Office of Planning

206-220-4460 (in Seattle)

From: ctpp-news-bounces@chrispy.net [mailto:ctpp-news-bounces@chrispy.net] On Behalf Of Lindeman, Nicholas (MPO)
Sent: Wednesday, June 06, 2012 1:22 PM
To: 'ctpp-news@ryoko.chrispy.net'
Subject: [CTPP] ACS/CTPP vs LEHD

I’ve sent the following query to both the ACS and CTPP but have not (yet) received a response. I was hoping someone on the mailing list might be able to provide assistance.

I’ve been working with Longitudinal Employer-Household Dynamics (LEHD)in On the Map. Specifically worker inflow/outflow analysis at the county level. I’ve discovered that there is a significant difference between the LEHD data and ACS Place of Work data from the 2008-10 3-Year ACS product. I've found that for the Middle Tennessee (Nashville) region the % of workers residing outside their home county is nearly 17 percentage points higher in the LEHD data than in the ACS data. Please see the attached table.

I've been tasked with determining the reason(s) for this difference. Any assistance you can provide would be greatly appreciated

Thank you,

Nick Lindeman

Nicholas Lindeman
Economic & Systems Data Analyst

Nashville Area MPO 
800 2nd Ave. S.

P.O. Box 196300
Nashville, TN 37219-6300
(615) 862-7198
lindeman@nashvillempo.org
http://www.nashvillempo.org