Hello Everyone:
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
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
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.
Thabet Zakaria
Deputy Director, Technical Services
Phone: 215-238-2885
Email: tzakaria@dvrpc.org
Fax: 215-592-9125