Wednesday, September 1, 2010

Long-form Census and the American Community Survey

I blogged earlier about how we use census data for urban and transportation planning and that the move from a mandatory long-form census to a voluntary system will affect data quality. Much has been said on the issue and a quick Google search will turn up lots of information.

In the US, they used to have a mandatory long-form census that went out every 10 years. People didn't like the long-form census and the US Census Bureau started the annual American Community Survey (ACS). Beta testing started in 1996 and the ACS went live in 2000. The 2010 US census was the first census without a long form. Unlike Canada, the US government spent 15 years transitioning to the ACS. The ACS is also mandatory; failure to complete the survey could result in a fine.

In 2003, the US Census Bureau tested a voluntary ACS and found that:
-A dramatic decrease occurred in mail response when the survey was voluntary
-The reliability of estimates was adversely impacted by the reduction in the total number of completed interviews
-The decrease in cooperation across all three modes of data collection resulted in a noteworthy, but not critical, drop in the weighted survey response rate
-The estimated annual cost of implementing the ACS would increase by at least $59.2 million if the survey was voluntary and reliability was maintained
-Levels of item nonresponse for the data collected under voluntary and mandatory methods were very similar
-The use of voluntary methods had a negative impact on traditionally low response areas, that will compromise our ability to produce reliable data for these areas and for small population groups such as Blacks, Hispanics, Asians, American Indians, and Alaska Natives
-The change to voluntary methods had the greatest impact on areas that have traditionally high levels of cooperation and on White and non-Hispanic households
In the end they kept the mandatory ACS. Since the Canadian government is going to a voluntary system, it will have to spend more money due to the cost of processing more forms and doing more followups to get data quality up. Either way, it is certainly going to be interesting in 2011 as there will be a new baseline for data trending which mean that information on transportation and other urban topics will not be able to be compared to 2006 or earlier data.

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