• Many ACS items refer to a time period different from that of the corresponding items on the long-form questionnaire: for example, usual hours worked per week, weeks worked per year, and income items on the ACS refer to the 12 months prior to the day when the household filled out the questionnaire, whereas these items on the long form always referred to the previous calendar year (1999 for the 2000 census).

  • The ACS currently includes three items not on the 2000 long form: (1) whether the household received food stamps in the previous 12 months and their value; (2) the length of time and main reason for staying at the address (for example, permanent home, vacation home, to attend school or college); and, for women ages 15–50, whether they gave birth to any children in the past 12 months.

Table 2-2 compares the items on the 2005 ACS questionnaire with the items on the 2000 census long form. The Census Bureau is proposing several changes to the ACS questionnaire beginning in 2008. These changes, if approved, will include the addition of three new questions on marital history, health insurance coverage, and veterans’ service-related disability, the deletion of the question on length of time and main reason for staying at the address, changes to the basic demographic items for consistency with the 2010 census questionnaire, and changes in wording and format to improve reporting of several other questions as determined by a 2006 test. A question on field of bachelor’s degree will be tested in 2007 and may be added to the ACS beginning in 2009.

Sample Design and Size

The ACS sends out questionnaires to about 250,000 housing unit addresses every month that have been sampled from the Census Bureau’s Master Address File (MAF; see Chapter 4 for details of the sampling operation). Each month’s sample includes addresses in every one of the nation’s 3,141 counties. The monthly samples cumulate to about 3 million addresses over a year, or about 2.3 percent of the total number of about 129.5 million housing unit addresses in the United States in 2005. The sample is constructed so that no housing unit address will be included more than once every 5 years.

The ACS sample is very large compared with the samples for major national household surveys. However, the long-form sample was even larger: in 2000, the long form was sent to about 18 million addresses, or one-sixth of total housing unit addresses in the United States at the time, and 16.4 million usable long-form questionnaires were included in the final edited data file. The ACS monthly and even yearly samples cannot be as large as

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