The figures presented in this paper were generated from tabulations of the March 1988, March 1992, and March 1997 Annual Demographic Files of the Current Population Survey (CPS). The CPS is a monthly survey of a sample of roughly 55,000 households nationwide. It provides information on the employment and unemployment status and other characteristics of the civilian population 16 years of age and older. In March, the CPS collects additional data from respondents in order to provide a more complete picture of each respondent's experience in the labor market (this is the Annual Demographic File). We created figures 1, 2, 3, 7, and 9 by tabulating the full CPS sample of individuals ages 16 and over who were not institutionalized or in the military. Appropriate sample weights were applied to the tabulations to arrive at the population estimates reported.
Each month, data on the hourly earnings of workers are collected from one-quarter of the CPS sample (see, for example, Mellor and Haugen 1986). The relevant questions are: (1) Is ____ paid by the hour on this job? (2) How much does ____ earn per hour?
Figures 4, 5, 6, and 8 were created by tabulating the one-quarter of the CPS sample who were questioned about their hourly earnings in March 1988, March 1992, and March 1997. Again, appropriate sample weights were applied to the tabulations to arrive at the population estimates reported. Because the population estimates underlying figures 4, 5, 6, and 8 are based on smaller samples than those underlying figures 1, 2, 3, 7, and 9, they have larger sampling errors associated with them.