Mechanism Sufficient Statistic in the Risk-Neutral Agency Problem

This paper analyzes the efficient use of information in an agency relationship with moral hazard, when parties are risk-neutral. We show that, given an arbitrary information system, all relevant information from a mechanism-design point of view can be summarized by a binary statistic. We then show that this allows a complete ordering of information systems for the risk-neutral agency problem. These results are obtained under a weak convexity condition which does not rely on an exogenous ordering on signal sets. The condition is shown to be more general than existing requirements for justifying the first-order approach.