[CTPP] Interesting Results from the ACS

The email shown reproduce below was posted by Thabet Zakaria. Because of the volume of spam/viruses in the last few weeks it inadvertently got snagged by our filtering system. I have reposted it below along with its original attachment.. MEMORANDUM Date: February 27, 2004 To: ctpp_news(a)chrispy.net From: Thabet Zakaria, Ph.D. Subject: Interesting Results from the ACS The recent e-mails to the cttp network are interesting. Dr. Edward L. Hillsman and his colleague have found out that the average 2002 commute time to work from the ACS for King County, WA was 5.7% lower than that obtained from the 2000 census. They also indicated that the average commute time over the two year period is down 10% in Washington, DC. Ed Christopher of the FHWA tells us that the Census Bureau is going to have a news conference to discuss new ACS data which show that Albany County residents have higher levels of education and household income than the average resident of New York state. These conclusions are based on the results of the ACS that was conducted nation-wide in the last several years based on a small sample of households. Last year, I reviewed the ACS estimates for the basic variables needed for transportation planning in the DVRPC region, which includes five counties in Pennsylvania and four in New Jersey and found the following: 1. The errors in the county estimates of population and employment are very large and cannot be compared to the Year 2000 census (about 6%). For example, the ACS underestimated the population of the City of Philadelphia, PA by 54,731 people. 2. The errors in the means of transportation to work estimates are even larger than those for population and employment (about 25%). For example, the standard error in the estimates of means of transportation for Mercer County, NJ ranges from 4.54 to 30.69% for workers who drove alone or took buses to commute to work, respectively. These erroneous findings are expected since the sample size is too small to produce comparable estimates to the Year 2000 census. Based on these results, we concluded that ACS estimates cannot be used for any of DVRPC’s transportation planning studies. The ACS estimates cannot be compared to the decennial census because the sampling errors in the ACS results are much higher. In summary, the current ACS results cannot be used to make rational conclusions for transportation planning analysis. TZ:ms