Screening settings, in which a profit-maximizing principal faces a privately-informed agent, have been studied extensively in the economics literature. A leading example is second-degree price discrimination with alternatives that correspond to different quantities or qualities of a product. In this case, it is natural to order the alternatives from worst (lowest quantity/quality) to best (highest quantity/quality) and to assume that the agent's private information concerns his marginal willingness to pay (for quantity/quality). This results in "increasing differences," which states that for any pair of alternatives, higher types are willing to pay more than lower types in order to obtain the better alternative instead of the worse one.