Money and the gains from trade*
研究在每次交易中双方恰好互相需要对方商品的环境里，货币如何影响交易效率。当交易者偏好不对称时，无货币经济会产生低效交易；引入货币后，若偏好不对称不太大，交易效率提高，且货币经济的贸易收益严格大于物物交换经济。
This article studies the role of money in environments where in each meeting there is a double coincidence of real wants. Traders who meet at random finance their purchases through current production, the sale of divisible money or both. It is shown that in the absence of valued money if traders have asymmetric tastes for each other's good, they produce and exchange socially inefficient quantities. With valued money, however, traders exchange efficient quantities if the asymmetry of tastes is not too large. It is shown that the gains from trade in the monetary economy are strictly greater than those in the corresponding barter economy, that the Friedman rule holds, and that the allocation of resources in the monetary economy converges to the allocation in the barter economy as the growth rate of the money supply is increased.