Part-time workers' earnings are much lower than those of their full-time counterparts, a difference often referred to as the part-time wage penalty. The mean hourly wage of part-time workers is only two-thirds that of full-time workers. Despite this wage penalty, there were no significant differences between part- and full-time workers in literacy skills and only modest differences in numeracy skills scores. This report uses new information about the literacy and numeracy skills of part-time workers to explore the connection between these skills and part-time workers' wages. The first section provides a descriptive review of part-time employment in the U.S. labor market, with emphasis on the part-time wage penalty among professional workers. It provides a unique perspective on the wage penalty as we can include not only measures of full- and part-time wages, but also full- and part-time worker literacy and numeracy skills. These issues are explored in this third paper in The Impact of Human Capital in the American Labor Market Series. The report, commissioned by the ETS Center for Research on Human Capital and Education, examines the association between wages and skills in the part-time labor market and is based on analysis of 2012-2014 data from the Survey of Adult Skills of the Programme for the International Assessment of Adult Competencies (PIAAC), an assessment measuring achievement in key domains, including literacy and numeracy, for countries across the world. Following up on the series' initial report, "Skills and Earnings in the Full-Time Labor Market. The Impact of Human Capital in the American Labor Market Series" (ED593028) which discovered a consistent and strong effect of literacy and numeracy skills on the wages of American full-time workers, the authors have found that, the overall effect of skills on the wages of part-time workers, too, were consistent and strong. They also found the skills of part-time workers to be similar on average to those of full-time workers, although wide variations existed among occupational sectors. [For the second report in the series, see "Skills and the Earnings of College Graduates. The Impact of Human Capital in the American Labor Market Series" (ED595423).]