The problem boils down to the fact that all definitions of money are arbitrary and that no single definition of money has a proven track record in terms of bearing a consistently close and predictable relation to the nominal GNP. There has been no consensus as to the best definition of money to targets. Indeed, some critics have argued that money is so undefinable, and that the velocity of money, however defined, is so unstable and unpredictable, that the Fed should consider using some alternative intermediate target.