Answer: Historical institutionalism is the hardest of the three streams to define because it includes so many different scholars and so many different methodological approaches. It is based on the assumption that institutional rules, constraints, and the responses to them over the long term guide the behaviour of political actors during the policy-making process. Historical institutionalism mixes the quantitative analysis of the rational choice stream with the idea- and culture-based thought of the sociological stream. It includes an eclectic group of scholars with a wide variety of research agendas.
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