THE VULNERABILITY OF 4 SOCIAL CHOICE FUNCTIONS TO COALITIONAL MANIPULATION OF PREFERENCES

The vulnerability of a social choice function to coalitional manipulat ion of preferences is defined as the proportion of voting situations i n which the social choice function can be manipulated by a coalition o f individuals. In this paper, we provide exact relations giving the vu lnerability of four specific social choice functions (plurality rule, anti-plurality rule, plurality with runoff, anti-plurality with runoff ) in three-alternative elections. Plurality with runoff appears to be less vulnerable than the other three rules.