In 2002 and 2003, the U.S. Census Bureau at the request of Congress, conducted research to determine whether the American Community Survey (ACS) could be implemented as a voluntary survey, rather than a mandatory survey. Working closely with staff of the Technology, Information Policy, Intergovernmental Relations and Census Subcommittee and the House Government Reform Committee, a test was designed to provide answers to key questions about the impact, if any, that a change to voluntary collection methods would have on mail response, survey quality, and costs. While the test was not a randomized experiment, the Census Bureau did conclude that:

• A dramatic decrease occurred in mail response when the survey was voluntary. The mail cooperation rate fell by over 20 percentage points and the final response rate after all three modes of data collection was about four percentage points lower. The reliability of estimates was adversely impacted by the reduction in the total number of completed interviews and a shift of a large number of interviews to the personal follow-up data collection mode.
• The estimated annual cost of implementing the ACS would increase by at least 38 percent if the survey was voluntary and the survey maintained the current reliability levels. (See Report # 3, Tables 13 and 14, pages 16-17.)
• Perhaps of greatest concern, the use of voluntary collection 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, and American Indians and Alaska Natives.

The original study does not assess if estimates produced from a voluntary ACS would differ from estimates from a mandatory ACS. A re-examination of the data that was collected in this test can help to answer this question.