A variable-production generalisation of Lerner's theorem

A government wishes to choose an optimal set of wage rates, but it is uncertain of individual characteristics. All it knows for certain is that each utility function is strictly quasi-concave and that the production function is linear. We assume that it can determine probability distributions, for each individual. of possible utility functions and ability levels. If each of these probability distributions is the same for every individual, expected social welfare is maximised by equalisation of wage rates. But since actual utility functions, and therefore labour supplies, will generally be unequal, incomes will then be unequal.