States cooperate in order to achieve certain goals better than they could without cooperation. Because the problems of noncooperation make cooperation a more attractive option, my study begins with the main features of an autonomous trade policy. I review four major dimensions along which trade policy may vary. Each dimension has received substantial attention in the existing literature, and each is interesting for some purposes. I am interested mostly in cross-national variation because cooperation involves two or more countries that may differ from one another. This stands in contrast to earlier work emphasizing variation in a single nation's tariffs from one good to another.

These first sections shows how various theories explain particular types of variation, clarifying which parts of it relate to the problem of variation in trade cooperation. Existing theories, especially in endogenous tariff theory (ETT), have provided an impressive explanation of variation in tariffs along some dimensions. For example, differences in industrial concentration or labor intensity explain variation in tariffs from one sector to the next. However, these variables do not explain international cooperation because they do not address cross-national variation in tariffs. However, clarifying the problem of variation in trade cooperation depends on explaining cross-national variation. The identities of countries, each with particular combinations of economic and political attributes (“grain-importing democracy”), shape cooperation.

The second half of this chapter builds on this analytical clarification by explicating different ways in which we can observe and measure trade policy.