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.