The growing number of interest groups active at the international level intrigues many political scientists. Most current explanations of global lobbying emphasize strategic incentives, such as venue-shopping, arguing that interest groups consciously choose to enter the international domain. Although strategic behaviour is undoubtedly present, available resources within the groups’ environment and institutional opportunities at the domestic and the international level systematically constrain and enable such choices. We draw on studies in US and EU interest group mobilization, and investigate the effects of such contextual factors for interest groups that enter the international domain. Our paper therefore offers an explanation for variation in the amount and type of interest groups that lobby at WTO Ministerial Conferences. We focus on the effects of domestic, economic, social and political variables, the political attention at the WTO for certain issues, and competition effects due to in- or decreased density of the WTO interest group population, and on the number of interest groups stemming from different countries and regions in the world. Our data-set containing about 2000 different organizations, allows us to identify which structural forces shape the strategic choices of interest groups that lobby at the international level.
