firm size-wage differentials, earnings functions, compulsory wage differentials, work characteristics

In their seminal study on interindustry wage differentials, Krueger and Summers (1988) expressed estimated industry differences as deviations from a hypothetical employment-share weighted mean. Virtually the whole labor literature has followed their approach, yet most studies avoid calculating the exact standard errors of these differences. This note relates this problem to the general literature on dummy variables and their interpretation. It is demonstrated that the implementation of exact estimates involves only simple matrix operations, making any approximative procedure difficult to justify. Disregarding this conclusion will in practice, even with large samples, lead to substantially overstated standard errors of the estimated differentials and to the understatement of their overall variability.

This paper compares technologies across space and time on the basis of factual and counterfactual substitution elasticities and argues that differences in estimated substitution elasticities should be decomposed into two counterfactual components. While the first component is designed to indicate how the ease of substitution is altered by varied economic circumstances, the second addresses the question of how technologies would compare under genuinely comparable situations. This argument is illustrated by the example of energy-price elasticities of capital before and after the oil crisis of the early 1970s.