However, these systems are actually more complex and the indirect
effects caused by co-products interaction in the international
market must be considered (Figs. 1 and 2). In the present study, a
ceteris paribus assumption was made, that is, the demand of the
functions fulfilled by another product is constant (Ekvall, 2000). It is
also assumed that agricultural production increases by area
expansion and not by intensification, since this would entail predicting
changes in type and amount of inputs required to increase
crop yields.