There are about 60,000 households in the sample for this survey. This translates into approximately 110,000 individuals, a large sample compared to public opinion surveys which usually cover fewer than 2,000 people. The CPS sample is selected so as to be representative of the entire population of the United States. In order to select the sample, all of the counties and county-equivalent cities in the country first are grouped into 2,025 geographic areas (sampling units). The Census Bureau then designs and selects a sample consisting of 824 of these geographic areas to represent each State and the District of Columbia. The sample is a State-based design and reflects urban and rural areas, different types of industrial and farming areas, and the major geographic divisions of each State. (For a detailed explanation of CPS sampling methodology, see
Chapter 1, of the BLS
Handbook of Methods.)
Every month, one-fourth of the households in the sample are changed, so that no household is interviewed more than 4 consecutive months. This practice avoids placing too heavy a burden on the households selected for the sample. After a household is interviewed for 4 consecutive months, it leaves the sample for 8 months, and then is again interviewed for the same 4 calendar months a year later, before leaving the sample for good. This procedure results in approximately 75 percent of the sample remaining the same from month to month and 50 percent from year to year.
Each month, 2,200 highly trained and experienced Census Bureau employees interview persons in the 60,000 sample households for information on the labor force activities (jobholding and jobseeking) or non-labor force status of the members of these households during the survey reference week (usually the week that includes the 12th of the month). At the time of the first enumeration of a household, the interviewer prepares a roster of the household members, including their personal characteristics (date of birth, sex, race, Hispanic ethnicity, marital status, educational attainment, veteran status, and so on) and their relationships to the person maintaining the household. This information, relating to all household members 15 years of age and over, is entered by the interviewers into laptop computers; at the end of each day's interviewing, the data collected are transmitted to the Census Bureau's central computer in Washington, D.C. (The labor force measures in the CPS pertain to individuals 16 years and over.) In addition, a portion of the sample is interviewed by phone through three central data collection facilities. (Prior to 1994, the interviews were conducted using a paper questionnaire that had to be mailed in by the interviewers each month.)