Productivity, Seniority and Wages. New Evidence form Personnel Data.

Wages may be observed to increase with seniority because of firm-specific human capital accumulation or because of self-selection of better workers in longer jobs. In both these cases the upward sloping wage profile in cross sectional regressions would reflect higher productivity of more senior workers. If this were true, the observation of an effect of seniority on wages would depend on the presence of controls for individual productivity. In this paper we replicate, using personnel data from a large Italian firm, the results of the pioneering work of Medoff and Abraham (1980 and 1981) in which supervisors' evaluations were used as productivity indicators. Since the validity of supervisors' evaluations as measures of productivity has been widely criticised, we extend the work of Medoff and Abraham using different direct measures of productivity based on recorded absenteeism and misconduct episodes. Both these indicators and supervisors' evaluation suggest that the observed effect of seniority on wages does not reflect a higher productivity of more senior workers. Theories in which wages are deferred for incentive or insurance reasons are therefore more likely to explain the observed upward sloping profile.