Inefficiency and Regulation in Credence Goods Markets with Altruistic Experts

We study a credence goods problem - that is, a moral hazard problem with non-contractible outcome - where altruistic experts (the agents) care both about their income and the utility of consumers (the principals). Experts' marginal rate of substitution between income and consumer utility declines in income, such that experts care less for consumers when their financial situation is bad. In a market setting with multiple consumers per expert, a cross-consumer externality arises: one consumer's payment raises the expert's income, which makes the non-selfish part of preferences more important and thereby induces the expert to provide higher quality services to all consumers. The externality renders the market outcome inefficient. Price regulation partially overcomes this inefficiency and Pareto-improves upon the market outcome. If market entry of experts is endogenous, price regulation should be accompanied by entry restrictions. Our theory provides a novel rationale for the widespread use of price and entry regulation in real-world markets for expert services.