Analysts of international politics can measure and explain the effect of international environmental institutions on the behavior of states and other actors and on the natural environment in three steps. First, we measure the outcome to be explained in terms of goal attainment, defined as the difference, over time or across cases, between actor behavior or the state of the natural environment on dimensions identified by institutional goals and certain end points determined by institutional goals. Second, we assess the effect of an institution in terms of the extent to which the existence or operation of the institution contributes, ceteris paribus, to variation in goal attainment. We transform these two variables into a score of institutional effectiveness to indicate the degree to which institutions contribute to the resolution of the environmental problems that motivate their establishment. Third, we analyze the relationship between institutional effectiveness and specific dimensions of institutional design—such as decision-making rules, membership and access conditions, and the compliance system.

Foreign aid often is interpreted as an international projection of domestic income redistribution mechanisms, and many authors suggest that differences between welfare states account for variations in donor behavior. A new understanding of the welfare state can improve traditional explanations of this linkage. Existing studies of the welfare–aid relationship use two welfare state indicators: domestic spending and partisan politics. We propose a third type of indicator—the institutional attributes of the welfare state—and demonstrate its relevance. The level of foreign aid provided by a country varies with social spending, but even more so with the degree to which its welfare state embodies socialist attributes. This finding helps explain how domestic political institutions influence the evolution of international cooperation and, specifically, how welfare principles institutionalized at the domestic level shape the participation of developed countries in the international aid regime.