Expansion of Preferential Trading Arrangements

The growing number of preferential trading arrangements (PTAs) since World War II has generated substantial interest in their economic and political effects. It has also prompted interest in the factors that give rise to PTAs, but very little research has been conducted on the growth of extant PTAs. To address this shortcoming, we analyze why some arrangements expand, whereas others do not. We find strong evidence that expansion is most likely when the existing members of a PTA display a high degree of trade openness and when the size distribution of these members is fairly uniform. We also find that PTAs that add new members are likely to do so again in the near future and that, throughout the global system, PTAs tend to expand in clusters. Equally, there is some indication that the market size of a PTA affects its odds of expansion. Finally, we investigate which states join enlarging PTAs. We find that PTAs expand by taking on new members that are economically and politically similar to existing members.