We show that Bayesian ex post aggregation is unstable with respect to refinements. Suppose a group of Bayesians use ex post aggregation. Since it is a joint problem, each agent's problem is captured by the same model, but probabilities and utilities may vary. If they analyze the same situation...

Tax competition (by states) and tax evasion (by individuals or companies) unfold at a dramatic scale. An obvious adverse effect is that some states lose their tax base. Perhaps less obviously, states lose out by setting tax policy differently – often reducing taxes – due to tax competition....