No nation can grow soy beans or corn more efficient and cheaper than the US which grows far more of these crops than the US ban consumes. China is the world leader in T-shirts manufacturing. It can produce vast amount of T- shirts at a lower cost than the US can make T-shirts. This competitive advantage makes sense got striking a trade between the US and China, in which the US exports to Chine soy beans and Chine exports to the US T-shirts is economically “win-win” satiation. Now there are 196 countries all wishing to trade. The mathematical formula as to how many potential number of bi-lateral trade agreements similar to the example I gve you above is 196! (196 factorial) which is a very very large number of potential bilateral trade agreements in which each side has something to gain.