According to a widely held belief, all who are able to work, should workʺ. We consider this statement within a framework of non-linear taxation. The crucial difference between our model and the standard model is that the government can distinguish between productive persons and the disabled. A...

In a less widely known contribution, Béla Martos (1966, Hungarian Academy of Sciences) introduced a generalized notion of concavity that is closely related to what is nowadays known as r-concavity in the operations research literature, and that is identical to what is nowadays known as...