The paper considers a voting model where each voter's type is her preference. The type graph for a voter is a graph whose vertices are the possible types of the voter. Two vertices are connected by an edge in the graph if the associated types are "neighbors." A social choice function is locally...

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...