In the multiple-partners job market, introduced in (Sotomayor, 1992), each firm can hire several workers and each worker can be hired by several firms, up to a given quota. We show that, in contrast to what happens in the simple assignment game, in this extension, the firms-optimal stable rules are neither valuation monotonic nor pairwise monotonic. However, we show that the firms-optimal stable rules satisfy a weaker property, what we call firm-covariance, and that this property characterizes these rules among all stable rules. This property allows us to shed some light on how firms can (and cannot) manipulate the firms-optimal stable rules. In particular, we show that firms cannot manipulate them by constantly over-reporting their valuations. Analogous results hold when focusing on the workers. Finally, we extend to the multiple-partners market a known characterization of the fair-division rules on the domain of simple assignment games.

Working Papers

We study an election under the influence of an interest group, assuming that a committee must decide between two options -- to implement a reform or to stay with the status quo -- and that all its members are aligned and in favor of the reform. The decision is taken via simultaneous voting and simple majority. An interest group that prefers the status quo offers an equal share of a ''small'' budget to any member that votes for against the reform. We demonstrate that even if the available budget is a miniscule fragment of the one required to buy the election for sure (Dal Bò, 2007), the interest group can be quite disruptive: there is always a completely mixed equilibrium in which the status quo is the most likely outcome, and the probability of its implementation converges to one as the size of the committee increases. The strategic uncertainty generated by the fact that other equilibria also exist, in which the reform is the most likely winner, seems to be the price that the interest group pays when attempting to buy an election for peanuts. We study the model under different assumptions on how the voting stage proceeds, but concerns on democratic quality do not vanish. 

A society of identical individuals must choose through elections one of two alternatives under uncertainty about the state of the world. Individuals can (a) choose the accuracy of their private signals about the state of the world at an increasing cost, and (b) send messages to other individuals to whom they are connected in some network. We show that the existence of a full network leads generically to two types of equilibria. First, there always exists an equilibrium in which only one citizen—a dictator—acquires information and everybody else votes equally based on such information, which is sent by the dictator to all other citizens via the network. Second, the only symmetric equilibrium that would exist without a network is also an equilibrium with a full network, but only if information acquisition costs are sufficiently high. This condition keeps at bay the extent of the positive externalities created by acquiring information that can be distributed at no cost. 

Work in Progress

Parties have been increasingly polarizing and spending in recent decades. How does this link with turnout? What is the role of mobilization and persuasion technologies? We study the effect of changes in technologies of mobilization (make people vote) and targeting (make people vote for me).

There is a strand of literature that compares information aggregation properties of simultaneous and sequential voting.  Even if intuitively sequential voting seems to favor information transmission, most works until now conclude in favor of simultaneous voting. A relevant paper in this sense is Dekel & Piccione (2000), which provides equivalence results between seuential and simultaneous voting. However, we show that if voters are allowed to abstain, sequential voting leads to full information equivalence in a broad class of binary elections.

We study a situation in which voters must decide whether to implement or not a reform. However, they are imperfectly informed about the adequacy of the reform, and they only get to see (individually) a signal about it before casting their vote. We show that if one of the alternatives is susceptible to not be implemented even if it wins the election, close elections might arise, which gives rise to aggregate uncertainty potentially playing a crucial role in the final outcome.