Knowledge that Transforms

We show that any well-behaved demand function can be represented by its “demand manifold,” a smooth curve that relates the elasticity and convexity of demand. This manifold is a sufficient statistic for many comparative statics questions; leads naturally to characterizations of new families of demand functions that nest most of those used in applied economics; and connects assumptions about demand structure with firm behavior and economic performance. In particular, the demand manifold leads to new insights about industry adjustment with heterogeneous firms, and can be empirically estimated to provide a quantitative framework for measuring the effects of globalization. (JEL F12, L11)

We establish new facts about the way consumers allocate debt among their credit cards using data for a representative sample of cardholders in Mexico. We find that relative prices are weak predictors of the allocation of debt, purchases, and payments. Consumers allocate a large fraction of their debt to high-interest cards, incurring a cost of 31 percent above the minimum. Using an experiment, we find that consumers do not substitute in the price margin, although they respond to salient temporary low-interest offers. We conclude that limited attention and mental accounting best rationalize our results and discuss implications for the market. (JEL D14, G21, O12, O16)