In the past, the study of international trade often focused on differences in labor, land and capital, as well as the distance between trading partners. But economists are increasingly looking at the role played by institutions, specifically those that enforce contracts and curb corruption.

We present a model with three blocks of nations: two of the blocks are members of a Customs Union (CU) and maintain a common external tariff (CET) on the third (non member). One of the member blocks is a block of new entrants. The producing lobby is assumed to be union-wide and lobbies...