Our analysis was conducted using employed SIPP sample members who were between ages 16 and 64 and who were not enrolled in school at the start of their jobs. We excluded students and older workers, because their labor market experiences are likely to be very different from those of the population that is the focus of this study.
Our analysis included information on those who worked for employers (that is, those who held jobs) and on those who owned businesses. At each wave, SIPP contains information on up to two jobs held by sample members and two businesses owned by sample members during the reference (four-month) period. Although the studies of low-wage workers reviewed in Chapter II typically examined those in jobs only, we included both jobs and businesses in our analysis, because a significant percentage of those with businesses were low-wage workers. For example, in March 1996, about 12 percent of all low-wage workers in our sample owned businesses, and an equal share of those with jobs and businesses were low-wage workers. Thus, we did not want to exclude from the analysis self-employed workers who constitute an important segment of the low-wage labor market.