A Recursive Measure of Voting Power with Partial Decisiveness or Efficacy

The current literature standardly conceives of voting power in terms of decisiveness: the ability to change the voting outcome by unilaterally changing one's vote. I argue that this classic conception of voting power, which fails to account for partial decisiveness or efficacy, produces erroneous results because it saddles the concept of voting power with implausible microfoundations. This failure in the measure of voting power in turn reflects a philosophical mistake about the concept of social power in general: a failure to recognize that an agent can exercise individual social power with others' assistance, in virtue of the group's collective power, sometimes even when she could not unilaterally scuttle the group's collective power. I therefore develop a conception of efficacy that admits of degrees and defend a Recursive Measure of voting power that takes partial efficacy into account.