The start of this turnaround could be associated with the other two trends, as the cumulative result of more favorable policies and increased labor per hectare, but it could also reflect the gradual spread of improved crop varieties that resulted from earlier investment in agricultural technology. The inflow of foreign aid to boost agricultural production did not rise until after the world food crisis of the 1970’s, and it peaked in the late 1980’s, yielding payoffs some years later.
此次转机的形成还与其他两种趋势有关，一是优惠政策和加大每公顷土地劳动力投入的累计效果，再有就是对农业技术早期投入所研制的改良作物品种的逐步推广。 在二十世纪七十年代世界粮食危机后提升农业生产的外国援助并没有更多流入，此类援助在二十世纪八十年代达到顶峰，并在若干年后开始产生回报。