In contrast, political scientists have rarely focused on explaining the pattern
of trade flows. Only some recent work has explored the political roots of import and export flows among countries. Moreover, political scientists have tended to see protection as the norm and have puzzled over why a country would ever liberalize its trade policy or adopt free trade. Politically, protec- tionism seems eminently reasonable. Explaining both protectionist and free trade policies and their changes over time has occupied political scientists. Indeed, the prevailing theories of the 1970s and early 1980s would have pre-
dicted the opposite of the rush to free trade. As I argue below, many systemic theories, such as hegemonic stability and dependency theory, seemed to fore- cast growing protectionism in the world economy. For many political scien- tists, then, the rush to free trade has been unexpected.
Here I explore four sets of issues that are central to understanding trade politics. First, what do we know about the preferences of domestic groups for protection or free trade? Why do some groups favor protection, and some favor free trade? Do these preferences change over time? And if so, why? Can changes in preferences explain the rush to free trade?
Second, how do political institutions affect the ways in which the prefer- ences of actors are translated into policy? How important are institutions in aggregating preferences and supplying policy? How much do changes in insti- tutions affect trade policy, and can they explain the rush to free trade?
Third, what factors at the international level shape trade policy choices? How do relations among countries and the structure of the international system affect domestic choices about trade? Have changes such as the end of the bi- polar Cold War system been responsible for the recent trend toward trade lib- eralization?
Finally, how does international trade itself affect states and the interna- tional political system? Do rising trade flows produce important changes in domestic preferences, institutions, and policies?
I examine each of these issues to see if they can provide us with some an- swers to the most significant aspect of trade policy today: the widespread liber- alization of trade policies that has taken place since the early 1980s.