We give a geometric interpretation of the lens condition, proposed by Deardorff as a shortcut for checking the factor price equalization (FPE) condition. We identify the conditions under which the lens condition implies the FPE condition. If the FPE zone is not a neighborhood of the diagonal...

We give two optimization programs for determining whether Pareto improving local changes are possible. When they are, the programs compute them. Any procedure generating efficient and Pareto improving changes can be replicated by these programs. The two programs are dual to each other. We apply...

We give a simple, constructive proof that the lens condition implies the factor-price equalization condition, when there are only two factors. Taking stock of the sufficient conditions under which the lens condition implies the FPE condition, we have the conditions of two factors or two goods or...

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

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....