Lower oil export earnings for OPEC countries have affected U.S. broiler exports; is there a lesson for the NAFTA renegotiations?We’ve long argued that the most important trade metric in macroeconomic terms is the overall volume of trade, not the balance of trade. Lower imports into the U.S. reduce exports in the long run because they decrease the purchasing power of trading partners. As the U.S. buys goods and services from other countries, it does so in U.S. dollars that can ultimately only be redeemed in the U.S. In short, capital flows move counter to trade flows, so a trade surplus means a deficit of capital inflows, while a trade deficit will lead to more capital inflows.Consider crude oil and broilers. OPEC member countries started ea...