A recurring theme in the literature on labor market structure is that different labor markets are characterized by different patterns of job mobility. For example, Doeringer and Piore (1971, p. 40) regard stability of employment as “the most salient feature of the internal labor market.” Kerr (1954, pp. 95-6) contrasts “structureless” markets that lack “barriers to the mobility of workers” with institutional markets in which entrance, movement, and exit are constrained by rules. Spilerman (1977) emphasizes career lines, noting how these may depend not only on personal characteristics but also on the occupation, industry, and firm of a person's port of entry.

Not everyone agrees that job shift patterns reflect differences in labor market structure. Some attribute these differences to various labor market imperfections: search costs (Oi, 1962), specific investments (Becker, 1964), uncertainty (Becker et al., 1977), and so forth. Others (e.g., Heckman and Willis, 1977; Doeringer and Piore, 1971, pp. 175-6) associate differences in job shift patterns with differences in workers: in nonmarket productivity, in preferences for leisure versus money and prestige, and so forth. Even those who attribute differences in job shift patterns to labor market structure do not agree on the boundaries of labor markets or on the reasons why occupants of certain kinds of jobs have similar job shift patterns.