"What does an income tax schedule look like, which takes account of the trade-off between equity and efficiency? This question was first asked by Mirrlees (1971) who developed the standard model of the optimal nonlinear income tax. Since then innumerable papers have generalized, refined, or corrected his analysis. It has also been realized that the second-best approach to income taxation pertains to a wide variety of economic problems such as monopoly pricing or contract theory in general. In this respect Mirrlees’ article has opened an important and fascinating strand of economic thought."