On September 8, 2006, I posted on this network, some comments on the
2005 ACS data on population and journey-to-work estimates for the
Delaware Valley region which consists of five counties in Pennsylvania
and four in New Jersey. In this email, I want to discuss the Delaware
Valley Regional Planning Commission's (DVRPC) experience with the 2005
ACS employed persons by place of work at the county level.
DVRPC uses census employed persons by place of work to develop the
number of jobs or employment. Employment data are used in the DVRPC
modeling process to estimate trip attractions by trip purpose. To
account for total employment, DVRPC factors upward census employed
persons by place of work to account for workers who have multiple jobs
and workers who were on vacation or sick during the survey days. DVRPC
has used this method successfully to develop employment estimates based
on the long-form of Census 2000.
The application of this method to 2005 ACS data on employed persons
produces erroneous results compared to those obtained from Census 2000.
The 2005 ACS employed persons by place of work results in reasonable
employment estimates for only three counties of the DVRPC nine counties.
Employment estimates for three of the remaining six counties are
significantly underestimated and three are overestimated. For example,
the employment estimate for Delaware County, PA is underestimated by
24,500 jobs or 10.3 percent compared to estimates from secondary
sources. Conversely, the employment of Burlington County, NJ is
overestimated by 16,300 jobs or 8.1 percent. These errors are expected
in the 2005 ACS results because of many reasons, including the ACS
sample size is too small, the population universe in estimated rather
than counted, and the data collection procedures are not comprehensive.
To produce reasonable employment data, DVRPC has used employment
estimates from other secondary sources such as BEA, BLS and ES 202.
Unfortunately, none of these sources can be used without adjustment.
BEA data have always been overestimated and BLS and ES 202 have always
been underestimated. Also, the margin of error in local employment
estimates is generally large. Hopefully, the planned accumulation of
ACS data for five years (2007-2011) may produce more accurate employment
estimates than the 2005 ACS data and data from secondary sources.
Deputy Director, Technical Services
Delaware Valley Regional Planning Commission
Philadelphia, PA 19106
New York State Data Center (SDC) staff (Leonard M. Gaines and Bob Scarmadalia) developed an excellent MS Excel spreadsheet tool to calculate statistical significance of differences and margins of error for calculations using data from the American Community Survey. Please feel free to use the worksheets in the attached MS Excel Spreadsheet (StatisticalCalculationsMenu_V21.xls).
Any feedback would be appreciated by NY SDC (LGAINES(a)EMPIRE.STATE.NY.US).
Continuing with the series of seminars on ACS, we have scheduled a
1-hour web-based session on tables from the American Community Survey.
Similar to the last seminar held in September, topics include:
1. A Short Update on the current status of the CTPP.
2. Accessing 2005 ACS data using the American Factfinder portal.
Date: Monday, December 18, 2006
Time: 2:00- 3:00 p.m. EASTERN
Connections: 50 (If we get more requests, we will try to get additional
For more information, please contact Nanda Srinivasan at ctpp(a)dot.gov
"ACS Training" Web Conference
Presented by Ed Christopher & Ken Bryson
Questions? Contact <mailto:NANDA.SRINIVASAN@DOT.GOV> Nanda Srinivasan,
202-366-5021 or <mailto:firstname.lastname@example.org> ctpp(a)dot.gov
The American Community Survey (ACS) was fully implemented in 2005.
Currently, data from the full implementation is available on the Census
Bureau's website for all areas in the U.S. with population of 65,000 or
higher. This training will help users understand ACS, and use the
American Fact Finder website to download and examine ACS data for their
December 18th 2006
2:00 p.m. (Eastern Time)
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