On the Number of alpha-Pivotal Players

We show that bounds like those of Al-Najjar and Smorodinsky (J. Econ. Theory, 2000) as well as of Gradwohl et al. (Math. Oper. Res., 2009) on the number of alpha-pivotal agents can be obtained by decomposition of variance. All these bounds have a similar asymptotic behaviour, up to constant factors. Our bound is weaker than that of Al-Najjar and Smorodinsky, but we require only pairwise independent—rather than independent—types. Our result strengthens the bound of Gradwohl et al.