We say that a social choice function is sensitive to collective change if whenever all inputs change, the outcome necessarily changes. Then, we prove that a social choice function is sensitive to collective change if and only if it is dictatorial. This provides a new interpretation of the...

The Pareto principle has great intuitive appeal, but poses perplexities on closer examination. What exactly do we mean by “preferences”? Should the principle apply ex post or ex ante? Does it uphold individual autonomy, individual welfare, or both? This essay argues that the Pareto principle...

In normative political theory, it is widely accepted that democratic decision making cannot be reduced to voting alone, but that it requires reasoned and well-informed discussion by those involved in and/or subject to the decisions in question, under conditions of equality and respect. In short,...

Agents frequently have different opinions on where to locate a public facility. While some agents consider the facility a good and prefer to have it nearby, others dislike it and would like to see it built far away from their own locations. To aggregate agents' preferences in these situations,...

Group identification refers to the problem of classifying individuals into groups (e.g., racial or ethnic classification). We consider a multinary group identification model where memberships to three or more groups are simultaneously determined based on individual opinions on who belong to what...

In college admissions and student placements at public schools, the admission decision can be thought of as assigning indivisible objects with capacity constraints to a set of students such that each student receives at most one object and monetary compensations are not allowed. In these...

We consider collective decisions made by agents whose preferences and power depend on past events and decisions. Faced with an ineffcient equilibrium and an opportunity to commit to a policy, can the agents reach an agreement on such a policy? Under an intuitive condition linking power...

Strategy‐proofness (SP) is a sought‐after property in social choice functions because it ensures that agents have no incentive to misrepresent their private information at both the interim and ex post stages. Group strategy‐proofness (GSP), however, is a notion that is applied to the ex...

We study the random assignment of indivisible objects among a set of agents with strict preferences. We show that there exists no mechanism which is unanimous, strategy-proof and envy-free. Weakening the first requirement to q-unanimity - i.e., when every agent ranks a different object at the...

We study the random assignment of indivisible objects among a set of agents with strict preferences. Random Serial Dictatorship is known to be only ex-post efficient and there exist mechanisms which Pareto-dominate it ex ante. However, we show that there is no mechanism that is likewise (i)...