Membership in customs unions (CU) has proliferated in past decades; globally, 81 countries are now part of a CU. Much of this growth has been driven by countries upgrading their links from a free trade agreement (FTA) to CU. At the same time, the rapid formation of new FTAs among countries that...

While “mega FTAs” and WTO-driven efforts at multilateral liberalisation dominate the agenda, customs unions (CU) are the silent success story of regional integration. Throughout the world, CUs have been superseding earlier FTAs, as new unions were formed or old ones expanded. Due to problems...