Economists have repeatedly warned against them, NGOs have fought them, and some governments have begrudgingly (at least in appearance) signed them. Yet, in the last twenty years the growth in number of preferential trade agreements (PTAs) has been unabated. Even more strikingly, their scope has broadened while their number was increasing. Deep integration provisions in PTAs have now become ubiquitous. Gaining market access or preserving existing preferences has remained an important motivation for acceding to PTAs. But with the liberalization of trade around the world and the related...