Let [gamma] = [partial]I/[partial]y > 0 be the marginal propensity to invest, [theta] = [partial]NX/[partial]y < 0 be the marginal negative trade balance effect (due to the marginal propensity to import), and [alpha] = [partial]S/[partial]y > 0 be the marginal propensity to save.

1]), is greater than the marginal propensity to invest out of income, I' ql (l/[F.