We initiate the study of naïveté-based discrimination, the practice of conditioning offers on external information about consumers’ naïveté. Knowing that a consumer is naive increases a monopolistic or competitive firm's willingness to generate inefficiency to exploit the consumer's mistakes, so naïveté-based discrimination is not Pareto-improving, can be Pareto-damaging, and often lowers total welfare when classical preference-based discrimination does not. Moreover, the effect on total welfare depends on a hitherto unemphasized market feature: the extent to which the exploitation of naive consumers distorts trade with different types of consumers. If the distortion is homogeneous across naive and sophisticated consumers, then under an arguably weak and empirically testable condition, naïveté-based discrimination lowers total welfare. In contrast, if the distortion arises only for trades with sophisticated consumers, then perfect naïveté-based discrimination maximizes social welfare, although imperfect discrimination often lowers welfare. If the distortion arises only for trades with naive consumers, then naïveté-based discrimination has no effect on welfare. We identify applications for each of these cases. In our primary example, a credit market with present-biased borrowers, firms lend more than is socially optimal to increase the amount of interest naive borrowers unexpectedly pay, creating a homogeneous distortion. The condition for naïveté-based discrimination to lower welfare is then weaker than prudence.

We analyse conditions facilitating profitable deception in a simple model of a competitive retail market. Firms selling homogenous products set anticipated prices that consumers understand and additional prices that naive consumers ignore unless revealed to them by a firm, where we assume that there is a binding floor on the anticipated prices. Our main results establish that “bad” products (those with lower social surplus than an alternative) tend to be more reliably profitable than “good” products. Specifically, (1) in a market with a single socially valuable product and sufficiently many firms, a deceptive equilibrium—in which firms hide additional prices—does not exist and firms make zero profits. But perversely, (2) if the product is socially wasteful, then a profitable deceptive equilibrium always exists. Furthermore, (3) in a market with multiple products, since a superior product both diverts sophisticated consumers and renders an inferior product socially wasteful in comparison, it guarantees that firms can profitably sell the inferior product by deceiving consumers. We apply our framework to the mutual fund and credit card markets, arguing that it explains a number of empirical findings regarding these industries.