A sender designs a signal structure to persuade a receiver to take an action. The sender is ignorant about the receiver's prior, and evaluates each signal structure using the receiver's prior that is the worst for the sender. I characterize the optimal signal structures in this environment. I show that there exists an optimal signal with two realizations, characterize the support of the signal and provide a formula that the signal must satisfy on the support, showing that the optimal signal is a hyperbola. The lack of knowledge of the receiver's prior causes the sender to hedge her bets: the optimal signal induces the high action in more states than in the standard model, albeit with a lower probability. I show that increasing the sender's ignorance can hurt both the sender and the receiver. If the sender is maximally ignorant about the receiver's prior on the states where the sender and the receiver disagree, then the optimal signal is continuous in the state and recommends the high action with a strictly positive probability in all states.
I study a model of multilateral bargaining in which multiple proposers simultaneously make offers on multiple pies. I show that there exist stationary equilibria with delay and characterize the equilibrium agreement sets. I establish that the worst equilibrium has a tractable geometric characterization and that in the worst equilibrium the agents agree if and only if the proposal power is sufficiently concentrated. I compare the efficiency consequences of different voting rules, showing that voting rules requiring approval by greater majorities lead to more delay in the worst equilibrium. I provide a characterization of the distribution of the proposal power that maximizes the agents' payoffs in the worst equilibrium, showing that this is the distribution under which the proposal power is concentrated to a moderate extent. Finally, I show that if the proposal power can be divided finely among the agents, then as the number of agents grows large, there are distributions of the proposal power such that in the worst equilibrium delay consumes almost all surplus.
I study a model of information aggregation in elections with multiple states of the world and multiple signals. I focus on a particularly simple class of equilibria -- threshold equilibria -- and completely characterize information aggregation within this class. In particular, I identify conditions on the distributions of the signals that are necessary and sufficient for information aggregation in every sequence of threshold equilibria, as well as simple conditions that are sufficient but not necessary for information aggregation in threshold equilibria. I also identify (generic) conditions that are necessary and sufficient for information not to be aggregated in any sequence of threshold equilibria. As a consequence, my analysis provides sufficient conditions for the existence of a sequence of equilibria that does not aggregate information.
We study a model of policy experimentation in organizations. Members have a common objective but differ in their prior beliefs about a risky policy. Current members collectively decide whether to experiment with the policy. Agents in the wider population possess resources of use to the organization and can enter and leave freely. We show that, for a wide range of parameters, there is too much experimentation. This is due to self-selection into the organization: unsuccessful experiments drive out conservative members, leaving the organization with a radical median voter who supports continued experimentation. When successes are imperfectly informative, these forces can sustain equilibria in which the organization experiments more when the policy is bad than when it is good. Our model can explain the survival of radical organizations which use tactics that repeatedly fail to achieve success. The model is applied to decision-making in environmental and civil rights organizations, non-profits and cooperatives.
Surrounded and Threatened: How Neighborhood Composition Reduces Ethnic Voting Through Intimidation (with Ted Enamorado).
“Why Vote for a Co-Opted Party? Endogenous Government Power Increases and Control of Opposition Politicians in Authoritarian Regimes.” Comparative Political Studies 50, no. 9 (2017): 1155–1185.