Social Movement Size, Organizational Diversity and the Making of Federal Law

During the 1960s and 70s the United States environmental movement experienced dramatic growth in both absolute size and in the diversity of organizational structures and issues represented within the movement. We assess the importance of change in movement size and compositional diversity on two important stages within the legislative process. Findings indicate that U.S. environmental movement size is positively associated with the incidence of Congressional environmental agenda-setting activities, but not the passage of environmental laws. An increased diversity of issue representation within the movement is consistently and positively associated with the incidence of agenda setting and law-passage activity. The growth of EMOs attending simultaneously to both traditional conservation and "new" quality of life issues, in particular, is associated with elevated rates of policy activity.