Can We Rule Out Speculative Hyperinflations in Maximising Models? Yes, We Can.

A critique is advanced of the contention of Obstfeld and Rogoff (1983) that in a fiat money regime, 'speculative hyperinflations can be excluded only through severe restrictions' on preferences. It is maintained here, in contrast, that no more than the infinity of the marginal utility of real balances at zero real balances is sufficient to rule out speculative hyperinflations. What Obstfeld and Rogoff have successfully drawn attention to is the theoretical possibility of money having strictly zero purchasing power. But the phenomenon of zero purchasing power has no explanatory power for historically observed hyperinflations, or any historically observed modern economy.