Food crops, exports, and the short-run policy response of agriculture in Africa
研究了14个非洲国家1975-1990年农业供给对价格变化的反应，发现粮食和出口作物在短期内是替代品，总产出对出口价格上涨反应为负，对粮食价格上涨为正，汇率对供给有显著影响。
The response of agriculture to changes in relative prices is an important factor in the success of structural adjustment programs in Africa. In this paper I estimate supply functions for total agricultural output, food crops and export crops in 14 African countries for the years 1975 to 1990. Food and export crops are substitutes in production in the short run. Total agricultural output responds negatively to increases in export prices and positively to increases in food prices. A plausible explanation is that as farmers shift resources to export crop production, food supply falls in the short run, while the increase in export supply may take several years to materialize. The exchange rate is significant in explaining both food and export crop production and aggregate agricultural supply, suggesting that the exchange rate is acting as a proxy for excluded macroeconomic variables or that changes in the exchange rate are not passed immediately through to prices.