The paper develops an explanation for the emergence of media of exchange through the unconcerted market behavior of individuals. Individuals are assumed to accomplish their ultimate exchanges through trading sequences which minimize the expected time spent searching for complementary trading partners. If individual perceptions of the trading environment are appropriately restricted, then the equilibrium pattern of trade will be some mixture of direct barter and use of a common good as medium of exchange. Although full monetization is always a locally stable exchange pattern, the economy may remain in universal direct barter or partially monetized states.

The preserving of flexibility when faced with uncertainty is a neglected aspect of behaviour under risk. Yet it is an important factor in decisions to hold liquid assets or delay irreversible investment. This paper formalizes the notion of flexibility in a sequential decision context, and relates its value to the amount of information an agent expects to receive. A rudimentary money demand model is developed embodying these ideas, and the history of flexibility as an economic concept is traced.

A model of the Treasury-bill futures market of the risk-premium augmented expectations variety is developed and estimated for the period March 1976 to July 1978. For that period we conclude that (1) futures interest rates deviate significantly from the corresponding forward rates implicit in the spot-market yield curve; (2) the hypothesis that expectations about the level of and trend in interest rates are formed adaptively from past spot rates fits the futures-market data significantly better than the hypothesis of perfect foresight; and (3) the risk-premium component of futures yields varies directly with time to delivery of the T-bills and negatively with the level of interest rates.