As a new concept in policy analysis, instrument constituencies shed light on the 'supply side' of policy-making and thereby fill a gap in our understanding of national and transnational policy dynamics. Policy instruments are not only 'active' because they contain scripts for reordering society but also because they gather a constituency comprised of practices and actors oriented towards developing, maintaining and expanding a specific instrumental model of governing. Instrument constituencies account for a hitherto neglected form of agency and explain the often-observed paradox that policy solutions sometimes chase policy problems, although the former are meant to emerge as answers to the later. We give an outline of the concept as it has been developed so far, formulate propositions, and discuss linkages with established research traditions in policy studies. 1 this definition includes policy instruments meant to achieve specific policy goals (e.g. market-based instruments for climate emissions reduction) but also instruments of the policy process, related to aspects such as orchestration and decision-making, impact assessment and evaluation, and to instruments of legitimation such as particular models of democracy, specific procedures of political representation, citizen participation or public relations.