This paper uses an infinite-horizon model based on individual maximizing behavior to study whether explosive price-level paths unrelated to monetary growth--speculative hyperinflations--can be equilibrium paths under rational expectations. In a pure fiat money regime, speculative hyperinflations can be excluded only through severe restrictions on individual preferences; but when the government fractionally backs the currency by guaranteeing a minimal real redemption value for money, speculative hyperinflations are impossible, even if agents are not completely certain that they can redeem their money in any given period. The analysis also confirms that implosive price-level paths and divergent paths for capital asset prices are not equilibria under either monetary regime.

Optimal monetary policy rules are derived in a rational expectations cum contracting framework. Monetary policy is redundant if wage setters exploit the incomplete current information embodied in today's nominal interest rate. However, the monetary authorities can save wage setters the costs of “indexing†to the interest rate. A contemporaneous money supply feedback rule is as effective as wage indexation. A lagged rule, relevant under a regime of money supply targeting, is also as effective if investors use the interest rate. Both rules have the same implications for the real interest rate as Poole's combination policy. However, the two rules have strikingly different implications for the nominal interest rate.

This paper uses an infinite-horizon model based on individual maximizing behavior to study whether explosive price-level paths unrelated to monetary growth--speculative hyperinflations--can be equilibrium paths under rational expectations. In a pure fiat money regime, speculative hyperinflations can be excluded only through severe restrictions on individual preferences; but when the government fractionally backs the currency by guaranteeing a minimal real redemption value for money, speculative hyperinflations are impossible, even if agents are not completely certain that they can redeem their money in any given period. The analysis also confirms that implosive price-level paths and divergent paths for capital asset prices are not equilibria under either monetary regime.