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. 

Work in Progress

Martinelli (2006) studies how much information would voters acquire ahead of an election; information providing a better knowledge on which is the right choice. We study how things change if (some) voters are connected. We see that if information is too costly, communication networks might have no effect.

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). However, we show that if voters are allowed to abstain, sequential voting leads to full information equivalence in a broad class of binary elections.