[CTPP] 2005 ACS Data Release

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 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. Thabet Zakaria Deputy Director, Technical Services Delaware Valley Regional Planning Commission Philadelphia, PA 19106 Phone: 215-238-2885 Email: tzakaria(a)dvrpc.org Fax: 215-592-9125