For many decades trade liberalization was the oil which allowed the engine of the global economy to run ever faster and more efficiently. It helped to fuel the long boom that followed the Second World War. Exports have grown thirty-five fold since then, thanks largely to a reduction in average tariffs from around 40% to 4% negotiated through the multilateral trading system, now embodied in the WTO. Despite this, some now question whether trade's role in supporting economic growth is...