Basic Monthly Survey Methodology and Documentation Page
Estimates from the CPS are based upon a probability sample of about 50,000 housing units. Each month, interviewers contact the sampled units to obtain basic demographic information about all persons residing at the address and detailed labor force information for all persons aged 15 or over.
To improve the reliability of estimates of month-to-month and year-to-year change, 8 panels are used to rotate the sample each month. A sample unit is interviewed for four consecutive months, and then, after an 8-month rest period, for the same four months a year later. Each month a new panel of addresses, or one-eighth of the total sample, is introduced. Thus, in a particular month, one panel is being interviewed for the first time, one panel for the second, ..., and one panel for the eighth and final time.
Interviewers use lap-top computers to administer the interview, asking questions as they appear on the screen and directly entering the responses obtained. The first and the fifth month-in-sample interviews are almost always conducted by an interviewer who visits the sample unit. Over 90 percent of month-in-sample 2 through 4 and 6 through 8 interviews are conducted by telephone, either by the same interviewer or by an interviewer working at one of 3 centralized telephone interviewing centers.
Completed interviews are electronically transmitted to a central processor where the responses are edited for consistency, imputations are made for missing data, and various codes are added. Based on the probability of selection, a weight is added to each household and person record so that estimates of the population by state, race, age, sex, and Hispanic origin match the population projections made by the Bureau of the Census each month.
To improve estimates of month-to-month change, a composite estimator is used that incorporates data from prior months. Many of the summary labor force estimates are also seasonally adjusted to facilitate month-to-month comparisons.
The latest detailed technical summary of CPS methodology is Technical Paper 63, which was issued in April 2000.
Basic Monthly Survey Methodology and Documentation Page
CPS Main Page