International trade and state efforts to liberalize or restrict trade generate very contentious politics. Trade creates winners and losers at the individual level, firm level, industry level, national level, and even regional level. It also generates conflict among transnational social groups, such as environmental advocacy organizations, human rights organizations, and transnational business alliances. Because of this complexity of the politics of international trade, scholars of international political economy (IPE) can focus on different levels of analysis and a variety of stages of the political decision-making process. Scholars agree that not only societal preferences but collective action problems, domestic institutions, and international factors all affect trade politics and policy outcomes. These aspects of trade politics together form the key influences on trade policy and whether it is liberal or protectionist in nature.
Societal preferences constitute the initial inputs into the trade policy-making process. Understanding how different groups of economic actors within society win or lose from trade liberalization or protection is the first step toward understanding trade politics and trade policy outcomes. Once societal trade preferences are formed, they must be aggregated into cohesive pressure groups or grass-roots movements whose purpose is to influence trade policy. This is easier for some groups of actors to achieve than others. In lobbying government actors on policy, interest groups find that domestic institutions play an important role translating societal inputs into policy outputs. Policy-making institutions vary in the degree to which they are susceptible to special-interest lobbying versus the preferences of broader societal coalitions, and electoral rules and party structures also affect policy outcomes, with certain configurations creating a bias toward more protectionism or liberalization.
In addition to these domestic-level influences on trade policy, IPE scholars have extensively studied the ways that international factors also affect trade policy outcomes such as the extent of liberalization and the content of what is liberalized (e.g., manufactures versus agricultural goods versus services). International factors such as the distribution of power, the character of international institutions and trade agreements (e.g., multilateral versus bilateral), transnational civil society and diffusion processes may be thought of as inputs into the policy-making process as well. Systemic conditions may constrain the types of policies that governments can adopt, or they may open the door to a range of possible policy outcomes that are nevertheless limited by the preferences of domestic societal actors.