The economic theory of Preferential Trade Agreements (PTAs), or discriminatory trade liberalization for and among a subset ofnations, was first analyzed with fun- damental and startling insight by Jacob Viner (1950). He destroyed the intuition that any move towards free trade was welfare-enhancing, for the country itself or for the world, or for both. He introduced us memorably to the notion of trade di- verting -- and here, he meant not diversion...