ing their high-school years and that many of them work during the school year. These surveys find a higher percentage of young people working than reported in the CPS. For example, one-third of 10th-grade and two-thirds of 12th-grade participants in the 1987 National Assessment of Economic Education Survey reported that they were employed at some time during the school year (Lillydahl, 1990). Surveys of parents of 16-to 18-year-olds in the nationally representative National Survey of Families and Households (conducted between March 1987 and May 1988) found that 70 percent of the teenagers had worked during the past month (Manning, 1990).
Surveys of representative samples of young people themselves, such as Monitoring the Future and the National Longitudinal Survey of Youth, give estimates that about 80 percent were employed at some point during the school year in their high-school years (Bachman and Schulenberg, 1992; Light, 1995; Steinberg and Cauffman, 1995). Such employment may begin early. Data from the National Longitudinal Study of Adolescent Health found that 30.6 percent of 12-year-olds worked during the school year, as did 36.9 percent of 13-year-olds, 35.4 percent of 14-year-olds, and 44.2 percent of 15-year-olds (Kruse, 1997). Table 2-2 shows the hours of work by 7th through 12th graders in this survey.
Early involvement in work may be associated with a greater amount of time spent working in later teen years. Schoenhals et al. (1997) found that students who worked more than 5 hours per week at a formal job during the school year as 8th graders had the highest labor-market participation rates of any group by 10th grade. They were more likely to be employed in 10th grade than those who had less or no work experience in 8th grade and, on average, they worked more than 20 hours per week when they were in 10th grade.
A number of factors may account for the discrepancies between data from CPS and data from survey results, and among surveys themselves. The employment questions sometimes refer to different periods of time (e.g., during the current school year, during the last month, during the last calendar year) and sometimes to employment at a single date (e.g., when the survey is administered). The longer the period of time under consideration, the higher will be the proportion of employed youngsters identified among those surveyed. In