Rate of arbitrage and reconciled beliefs

Abstract : Any group of risk neutral agents who hold differing beliefs is vulnerable to money pumps (arbitrage). Thus, the agents may wish to reconcile their beliefs into a new joint belief. We propose a criterion for the choice of reconciled belief based on the notion of ``rate of arbitrage.'' It is shown that there exists a unique belief (probability distribution) that minimizes the maximal expected rate of arbitrage, and an explicit formula for this belief is given.