Approval Voting and Arrow's Impossibility Theorem

Approval voting has attracted considerable interest among voting theorists, but they have rarely investigated it in the Arrovian frame-work of social welfare functions (SWF) and never connected it with Arrow's impossibility theorem. This note explores these two directions. Assuming that voters have dichotomous preferences, it first characterizes approval voting in terms of its SWF properties and then shows that these properties are incompatible if the social preference is also taken to be dichotomous. The positive result improves on some existing characterizations of approval voting in the literature, as well as on Arrow's and May's classic analyses of voting on two alternatives. The negative result corresponds to a novel and perhaps surprising version of Arrow's impossibility theorem