Optimal Contracts, Adverse Selection & Social Preferences: an Experiment

It is standard in agency theory to search for incentive-compatible mechanisms on the assumption that people care only about their own material wealth. Yet it may be useful to consider social preferences in mechanism design and contract theory. We devise an experiment to explore optimal contracts in an adverse-selection context. A principal offers one of three possible contract menus to a team of two agents of unknown types. We observe numerous rejections of the more lopsided menus, and approach an equilibrium where one of the more equitable menus (which one depends on the reservation payoffs) is proposed and agents accept a contract, selecting actions according to their types. We estimate the Fehr and Schmidt (1999) and Charness and Rabin (2002) models of social preferences with our data, and calculate ex post optimal socialpreference contracts. In both cases, the principal could substantially enhance his profitability if he could offer the derived optimal contract menu. We also find evidence that an agent is substantially more likely to reject a contract menu if her teammate rejected a contract menu in the previous period, suggesting that agents may be learning social norms.