If this finding is correct, then in less-favored areas like the Zona da Mata, focusing research and agricultural extension services on particular categories of farms or farm sizes is unlikely to yield greater returns than treating all farms alike. No positive long-term trends in modern input use were evident during this research. This implies that supply constraints, particularly credit constraints, may be a primary determinant of technology adoption, and that these supply constraints affect almost all farms equally. A number of farms radically altered their output mix during the period, suggesting that agro-ecological factors played a limited role in determining product mix, even in an ecologically diverse region like the Zona da Mata. It can be taken as a positive sign, however, that even Brazil's poorest farmers were willing and able to make changes in product mix and production technique in response to economic and other incentives.
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