A standard hidden information model is considered to study the influence of the a priori productivity distribution on the optimal contract. A priori more productive (hazard rate dominant) agents work less, enjoy lower rents, but generate a higher expected surplus.

Contract theory predicts that workers are remunerated based on all available unbiased individual performance measures. In the real world, measures are often biased: tasks are too complex to include all measures, unforeseen contingencies occur for which contracts specify nothing, and the...