A study published in the August 2008 issue of the "American Journal of Agricultural Economics", found NAFTA increased US agricultural exports to Mexico and Canada, even though most of the increase occurred a decade after its ratification. The study focused on the effects that gradual "phase-in" periods in regional trade agreements, including NAFTA, have on trade flows. Most of the increases in members' agricultural trade, which was only recently brought under the purview of the World Trade Organization, was due to very high trade barriers before NAFTA or other regional trade agreements.