Modern neoclassical approaches to labor markets frequently emphasize dynamic processes rather than static ones. The dynamic view of unemployment, for example, stresses labor turnover in understanding disequilibrium in labor markets (Robert E. Hall, 1972). Job instability, spells of unemployment, the flow of workers into and out of unemployment are some of the aspects of the dynamic view. Empirical research in this area (and others with a dynamic orientation) is usually based on longitudinal panel surveys which record the labor force transitions, or changes in labor force status, of persons over time. Unfortunately, longitudinal surveys are not numerous because they are expensive and difficult to conduct. The primary sources of labor force transition data, for example, have been the National Longitudinal Surveys, the Panel Survey of Income Dynamics, and the longitudinal subfiles from the Current Population Survey (CPS).