Manipulation via information in large elections

Abstract

This thesis studies manipulations of equilibria by candidates in two-alternative elections along with their effects on voter turnout, winner of the election and social welfare where voters have common values, and both voting and manipulating are costly. We show that manipulation is not desirable for the society, and the candidates’ incentives for manipulating can be mitigated by appropriately sequencing the order of manipulations. We present some results of a manipulation game which may rather unexpected under the assumption that the candidates have prior beliefs about each others’ manipulations. Finally we determine the set of manipulations which can be prevented by informed voters for a given composition of society.