[Excerpt] To say that part-time workers are less costly than full-time workers, however, is not an explanation for the trend in the use of part-time employees that has occurred. Rather, one must show that the relative cost advantage of part-time workers has increased over time and that variations in the relative cost advantage are associated with variations in the usage of part-time employment. Somewhat surprisingly, few researchers have tried to do this, and even these only indirectly. This paper addresses this issue, albeit in a slightly different way, focusing on data from the United States. We begin in the next section by analyzing data on part-time employment in the United States. After controlling for cyclical factors, an increasing trend in the usage of part-time employment is observed. Moreover, it is clear from the component of part-time employment that is increasing that this is a demand-side, not a supply-side phenomenon.