We study a multi-dimensional collective decision under incomplete information. Agents have Euclidean preferences and vote by simple majority on each issue (dimension), yielding the coordinate-wise median. Judicious rotations of the orthogonal axes -- the issues that are voted upon -- lead to...

Which decision rule should we use to make a binary collective choice? While voting procedures are applied ubiquitously, they are criticized for being inefficient. Using monetary transfers, efficient choices can be made at the cost of a budget imbalance. Is it optimal to do so? And why are...

We study the effects of allocative and informational externalities in (multi-object) auctions and related mechanisms. Such externalities naturally arise in models that embed auctions in larger economic contexts. In particular, they appear when there is downstream interaction among bidders after...