We give two procedures for determining whether efficient Pareto improving local changes are possible. When they are, the procedures compute for them. Any procedure generating efficient and Pareto improving changes can be replicated by these procedures. The two programs form a striking duality....

We introduce technological differences in a Heckscher-Ohlin model and study how the technology and endowment differences interact to determine the effects of trade on factor prices. When the endowment effect is dominant in determining the autarky relative factor prices, the relative factor...