New Institutionalism (NI) has been an influential project in social science theory for over 40 years, with major impacts on disciplines as diverse as political science, sociology, economics, and geography. All NIs include a much wider range of phenomena - including formal rules, shared norms and understandings, and standard operating practices - in their definition of institutions than did the old institutionalism. The old institutionalism was criticized as being largely descriptive, without any compelling theoretical framing. Hall and Taylor's seminal paper of 1996, a division into three main branches of NI has been widely followed: sociological institutionalism (SI), historical institutionalism (HI) and rational choice institutionalism (RI). While RI draws on neoclassical economic models of rational actor behavior, SI and HI focus on the social construction of knowledge, power, and rules. A major focus of RI is to develop models of individual political motivation and action that can be aggregated to understand the actions of political actors at larger scales.