Instrument constituencies and public policy-making: an introduction

Abstract For many years, policy-making has been envisioned as a process in which subsets of policy actors engage in specific types of interactions involved in the definition of policy problems, the articulation of solutions and their matching or enactment. This activity involves the definition of policy goals (both broad and specific), the creation or identification of the means and mechanisms that need to be implemented to realize these goals, and the set of bureaucratic, partisan, electoral and other political struggles involved in their acceptance and transformation into action. While past research on policy subsystems has often assumed or implied that these tasks could be undertaken by any actor, more recent research argues that distinct sets of actors are involved in these three tasks: epistemic communities that are engaged in discussions about policy dilemmas and problems; instrument constituencies that define and promote policy instruments and alternatives; and advocacy coalitions which compete to have their choice of policy alternative and problem frames adopted. Two of these three sets of actors are quite well known and, indeed, have their own literature about what it takes to be a member of an epistemic community or advocacy coalition, although interactions between the two are rarely discussed. The third subset, the instrument constituency, is much less known but has from the outset been considered in relation to these other policy actors. The articles in this special issue focus on better understanding the nature of actor interactions undertaken by instrument constituencies and how these relate to the other kinds of actors involved in policy-making.


Introduction
In much of the policy research published in recent decades, the principle actor many policy theorists argue is central to policy-making is the 'subsystem' or policy 'community' (McCool, 1998;Sabatier, 1991). This is typically defined as a mostly undifferentiated group of actors originating in widely different areas of state and society who are united by a mutual KEYWORDS advocacy coalition framework; instrument constituencies; epistemic communities; multiple streams framework; policy formulation; policy subsystems concern for, and knowledge of, a specific policy area. They are not necessarily self-interested but share some ideas and knowledge about the policy area in question, which sets them apart from other policy actors (Howlett & Cashore, 2009;Howlett, Ramesh, & Perl, 2009;Kingdon, 2011).
These sets of actors go by a variety of different names -policy networks, policy communities, issue networks, and the like -but the general 'subsystem family of concepts' emerged in the 1950s to better explain the role of discourses and interest in the policy-making process. These ideas acknowledge the complex informal and formal exchanges that take place between both state and non-state policy actors and improve on previous work that emphasized material, self-interested activity on the part of a more limited range of actors involved in formal policy deliberations, such as think tanks, interest groups, lobbyists, bureaucrats and politicians (McCool, 1998). Early studies on these policy actors were seminal in the discipline and included the articulation of a wide array of often competing concepts and terminology to describe such collectivities, such as 'iron triangles' , 'sub-governments' , 'cozy triangles' , 'power triads' , 'policy networks' , 'issue communities' , 'issue networks' , 'advocacy coalitions' , 'policy communities' and others. All these terms refer to the propensity of policy actors to create alliances surrounding substantive issues that traverse institutional boundaries and join together both governmental and non-governmental actors in groups sharing similar perspectives on policy issues, problems and solutions (Arts, Leroy, & van Tatenhove, 2006;Freeman, 1997;McCool, 1998).
Subsystem theory helped distil the often informal connections between actors, ideas, interests and institutions that earlier policy studies had largely ignored when they focused on the more formal institutional linkages that exist between governmental and non-governmental agents active in policy-making McCool, 1998). The concept of 'subsystem' was more nuanced than other terms in that it merged actors, ideas and institutions together, allowing policy scholars to more precisely identify the main actors in a policy process, what connects them, how they interact with each other, and what effect their interactions have on policy results (Freeman & Stevens, 1987;).
Such a unified or undifferentiated conception of a policy subsystem, however, is problematic on several scores. As shall be argued below, in particular, the grouping of all policy actors together in a single policy subsystem has improperly and confusingly juxtaposed similar but distinct policy-related collective actors involved in activities such as problem definition, policy formulation, and policy bargaining and conflict. This situation has obscured the importance and activities of such actors in policy processes.
For example, recent works have highlighted how some specific sets of actors -the 'epistemic communities ' Haas (1992) and others identified -such as marine biologists and other scientific experts working in the area of oceans policy focus exclusively on problem definition, rarely venturing into the realm of policy instruments of solutions (Rudd, 2014). Other research has highlighted the significant roles 'advocacy coalitions' -the configurations of actors Sabatier (1987Sabatier ( , 1988 who are identified engaged in policy-making debates but who have different visions of those policies -have played in contesting and enacting preferred policy programmes and alternatives, mainly in the political realm rather than throughout the entire policy process (Jorgensen, 2017).
While this research on advocacy coalitions and epistemic communities has been undertaken since the mid-1990s and has advanced our understanding of these aspects of policymaking, the third leg of this triad, the 'instrument constituency' , is much less known and understood, having emerged only recently, as seen in Voss and Simons (2014) and Mann and Simons (2014) case studies of European environmental and social policy-making. The idea that a third major collective actor in the policy process who is concerned exclusively with the articulation and promotion of policy solutions exists provides an answer to what was previously a missing link in the study of policy actors and policy processes and helps answer several important questions that previously stymied scholars of policy formulation processes (Béland & Howlett, 2016). This special issue of Policy and Society focuses on instrument constituencies and how they are different and distinct from the other kinds of actors found in a policy subsystem, and how these different elements interrelate and interact with each other in the process of policy formulation. This approach allows for the possibility of separate deliberations on policy tools, deliberations conducted autonomously from considerations of the political or problem context, both spatially and temporally. The essence of policy-making in this view consists less in identifying new solutions once problems have been defined, as many existing studies and textbooks would have it, but rather matching those definitions to previously existing solutions.
This introductory article provides a brief overview of the various contributions to this special issue but also suggests that the concept of instrument constituencies allows for a fundamental rethinking of many aspects of policy theory based on subsystem concepts. We argue that distinguishing clearly between these three sets of actors and activities allows researchers and practitioners to better capture how policy problems are designated and defined and how they move forward through the political processes. Kingdon (1984) was the first to suggest dividing policy-making into separate sets or streams of actors. This view of a more differentiated subsystem in which specific roles and activities are assigned to specific sets of actors helps develop a comprehensive framework of analysis that can, first, establish patterns that catalyze action from one phase of the policy process to another and second, analytically unpack the 'black box' of each phase, introducing a more subtle and dynamic view of policy-making than was typically found in older analyses .

Collective actors in policy-making and their activities: the advantages of separating subsystems into distinct streams
Emphasizing the contingency of the processes that lead to policy decision-making, Kingdon premised his work on the 'garbage can' theory of organizational choice to try to understand how some issues raise in importance in ambiguous policy contexts depending on the actions of different sets of actors (Cohen, March, & Olsen, 1972;March & Olsen, 1979). As is well known, in order to better model agenda-setting activities in the United States, Kingdon (1984) framed agenda-setting as a set of activities undertaken within a single policy subsystem. He emphasized the role played by particular actors -'brokers' or 'policy entrepreneurs' -who were able to garner support for specific issue definitions and endorse the importance of particular issues among other subsystem members.
But Kingdon also proposed three independently flowing 'streams' of events in which subsystem actors were active: the political, policy and problem streams. These streams were brought together by focusing events and often unexpected windows of opportunity to elevate policy items from the unofficial or public agenda onto the government one. This interpretation of policy actors was sufficient for Kingdon's analysis of agenda-setting processes centred on an understanding of how a policy 'situation' moved from the 'policy universe' or undifferentiated public, social sphere of policy attention to become a defined policy 'problem' . That is, Kingdon's (1984) work helped to show how such subsystems worked to narrow possible agenda items to the much smaller number that receive formal governmental attention.
The idea of streams, or the series of events involved in different aspects of this process, however, fit awkwardly with the concept of an undifferentiated subsystem. For Kingdon (1984), defining or framing an issue or condition is a key activity in the policy process, one that transforms an issue into a problem that policy-makers can address. The pairing of problem definition and policy alternative is what causes an issue to be included in the government agenda in the multiple stream framework (MSF). However, as Knaggård (2015, p. 452) notes, in Kingdon's work, this joining conflates two very distinct activities, whereby 'coupling becomes the same act as defining problems' and inhibits a clearer understanding of how policy entrepreneurs are enabled or constrained by the contexts in which they work to promote certain problem definitions and not others. Demarcating epistemic actors who are concerned primarily with policy issues and problem framing helps to bring about analytical clarity to this particular aspect of policy-making activities. That is, while his notion of brokers or entrepreneurs helped to recognize how problem definitions and solutions were paired, Kingdon (1984) was unclear about who exactly was involved in defining and selecting one or more alternatives over others or in framing a problem in one fashion rather than in another.
The lack of detail in the conception of agency in Kingdon's original model has left a major gap in existing works about the policy process that are based on his framework (Cairney & Jones, 2016). Without a clearer conceptualization of agency, it is difficult to see how essential phenomena such as streams of intersecting events cause agenda items to 'move forward' in practice (Hood, 2010;Howlett, 2012). This is especially significant for those wishing to take the multiple streams framework forward to cover policy-making stages beyond the initial ones. As Howlett, McConnell, and Perl (2015) have shown, many of these authors have simply carried forward the idea of a three-stream confluence remaining in place following the agenda-setting stage in order to refer to activities occurring at subsequent stages of the policy process (Teisman, 2000). Others, however, have suggested that after an item enters the formal agenda, at least some of the streams split off once again to resume their parallel courses (Teisman, 2000;Zahariadis, 2007). Yet others have suggested that additional streams emerge and become visible through and beyond agenda-setting, such as those involved in operational administrative processes once a problem has been established during agenda-setting Zahariadis, 2007).
Hence, although insightful with respect to agenda-setting, Kingdon's (1984) initial framework requires some revisions and additions to help address policy formulation (e.g. Béland & Howlett, 2016;Howlett et al., 2015). That is, generally stating that multiple streams and multiple phases of policy-making exist, as scholars basing their work on Kingdon's (1984) lead have often done, begs the question of how the processes Kingdon (1984) identified are actually carried out by policy agents. To be more analytically meaningful about the policy-making process, work in this vein needs to directly address questions about the nature of the streams Kingdon (1984) identified, including how they originate, operate and evolve.
In particular, two major questions must be addressed if the MSF is to provide a workable model of the policy-making process (Mukherjee & Howlett, 2015): (1) How can the various streams of events and activities involved in policy-making be operationalized to be able to distinguish them analytically from each other and analyze their interactions during different phases of the policy process? (2) How can the separation and coming together of one or more of the streams before, after and during different phases of policy-making activity be analyzed in relation to these actor relationships?
Exploring how the streams metaphor can be better visualized to incorporate more precise notions of agency is key to advancing the work of better comprehending policy formulation. Studying how each stream operates and how subsets of actors within the policy subsystem interact with or disconnect from each other during the course of the policy-making process, affecting both the timing, content and impact of policies, is critical. It is at this juncture that adding the concept of an instrument constituency to those of epistemic communities and advocacy coalitions is most helpful (Mukherjee & Howlett, 2015).

Disaggregating the policy subsystem
Viewing a subsystem as composed of distinct subsets of actors engaged in specific policy, problem and political tasks is a better way of understanding how policy streams interact in policy-making than adopting a more traditional, undifferentiated subsystem conception (Mukherjee & Howlett, 2015). In this view, responsibility for the range of tasks to be performed in articulating policy, developing and advocating means to achieve these policies, and ultimately making deciding about them falls upon three distinct sets of subsystem actors: experts in the knowledge area concerned, experts on policy tools and authoritative decision-makers and their colleagues, respectively . Although these sets of actors can overlap, locating each of them within a distinct policy stream allows us to map the policy subsystem better than lumping them together into one unit. Hence, within the policy subsystem of actors defining a particular policy arena such as national environmental policy, it is possible to see one group of policy actors involved in a subject area such as climate change as working towards defining the nature of the problem governments must address. This group exists and functions independently from constituencies that form around particular instruments (for example, those favouring tradable pollution permits) and from coalitions of actors in key institutional venues and agencies that hold a variety of beliefs regarding factors such as the legitimate role of government in society or the degree to which public opinion will support certain definitions and courses of action that are involved in the political aspects of policy-making.
Re-conceptualizing streams as being comprised of distinct gatherings of policy actors within a subsystem allows each different subgroup to be analyzed as a discrete entity rather than being obscured within the multiple tasks undertaken by the subsystem as a whole. This is not to say that these different groups cannot share some membership across a range of activities. Rather, it allows internal activity within each subset to be clearly distinguished from activities that occur between them as subsystem actors engage each other to various degrees and in different forms throughout the policy-making process.

Synthesizing the existing literature and filling in the gaps
As mentioned above, some of these actors have already been examined in some depth in the policy sciences literature or in literature in other fields, such as international relations, while others have not. This means advancing thinking and theory in this area requires both appropriating and synthesizing the existing literature on these groups (i.e. advocacy coalitions and epistemic communities) and developing and then integrating research findings on the missing links (i.e. instrument constituencies). This is what this special issue sets out to accomplish.

Agents in the problem stream: epistemic communities
While it would be possible, in answering the question about who is active in policy formulation and what they do, to develop new terminology to describe each subgroup, adequate terms already exist in the policy literature that can be used for this purpose. In this light, as discussed in more detail below, the concept of epistemic communities, which emerged out of the international relations literature to identify groups of scientists involved in defining and delimiting problem spaces in areas such as oceans policy and climate change (Gough & Shackley, 2001;Haas, 1992;Zito, 2001), can be used as the basis for understanding the first set of actors involved mainly in defining policy problems.
Academic explorations of epistemic communities has thus far been mainly through examples from environmental policy, a field that is constantly engaged in connecting scientific findings to policy-making. Haas (1992) first described the epistemic communities involved in deliberations in the environmental sector as a diverse group of policy actors including scientists, academics experts, public sector officials and other government agents who are united by a common interest in or a shared interpretation of the science behind an environmental dilemma (Gough & Shackley, 2001;Haas, 1992). These epistemic communities, he found, influenced 'policy innovation not only through their ability to frame issues and define state interests but also through their influence on the setting of standards and the development of regulations' (Adler & Haas, 1992, p. 378).
Information regarding a policy problem is the glue that bonds actors within an epistemic community together, differentiating them from those actors involved in political negotiations and practices around policy goals and solutions, as well as from those, discussed below, who specialize in the development, design and articulation of policy tools or solutions (Biddle & Koontz, 2014). Several studies exist supporting this view of the perceptions of epistemic community members and the problem-framing role they play in policy-making (Lackey, 2007;Meyer, Peter, Frumhoff, Hamburg, & de la Rosa, 2010;Nelson & Vucetich, 2009). In his studies of global oceans research and policy, Rudd (2014Rudd ( , 2015, for example, provides important empirical findings related to scientists' framing of environmental dilemmas at the science-policy interface. In his large-N, quantitative study spanning 94 countries and meant to comprehensively cover the role of scientists in oceans policy-making, Rudd points out conclusively the uniformity regarding research priorities across the globe. He writes that, once evidence is assembled and knowledge created, it must also be effectively communicated, sometimes in politicized environments, ensuring that it is effectively brought to bear on sustainability challenges. Demands on scientists to increase the level of integration and synthesis in their work, and to communicate increasingly sophisticated information to policymakers and society, will only grow. (Rudd, 2015, p. 44) How these actors engaged in problem-defining, from scientists to political partisans and others depending on the case, are active beyond agenda-setting and into policy formulation and how they are engaged in discussions within the problem stream that led to the definition of broad policy issues or problems (Cross, 2015;Hajer, 1997Hajer, , 2005Knaggård, 2015) are key issues in the field, and several of the essays in this special issue address this topic.
In the agenda-setting stage of the policy process, for example, epistemic communities are critical in leading and influencing the activities of other actors by defining the main direction the policy process takes. This path-dependent evolution of problem definition indicates, as Adler and Haas (1992) noted, that 'the effects of epistemic involvement are not easily reversed. To the extent to which multiple equilibrium points are possible … epistemic communities will help identify which one is selected' (Adler & Haas, 1992, p. 373).This, in turn, could have a heavy impact on the policy deliberations that follow and other activities at later points in the policy process. However, more study is required to see exactly if and how this activity emerges.

Actors in the policy stream: instrument constituencies
Epistemic Communities are distinct from the second group of actors, instrument constituencies, whose focus is much less problems than solutions. 'Instrument constituencies' is a term recently developed in the comparative public policy field to describe the set of actors involved in solution articulation, independent of the nature of the problem to be addressed (Voss & Simons, 2014).
The policy instruments that are devised or revised, considered, and assessed in the process of matching problems and solutions can also usefully be viewed as the cognitive constructs of specific sets of social policy actors as they grapple with policy-making. Such constituencies advocate for particular tools or combinations of tools to address a range of problem areas. They are hence active in the 'policy' stream Kingdon (1984) identified, one that increases its activity as policy alternatives and instruments are formulated and combined to address policy aims.
Not to be conflated with advocacy coalitions or epistemic communities, these actors are united by their adherence to the design and promotion of specific policy instruments as the solutions to general sets of policy problems, usually in the abstract, which are then applied to real-world conditions. Unlike epistemic communities that pursue the translation of broad issues into distinct problems that policy-makers can act upon, instrument constituencies are more concerned with policy tools and supplying policy-makers with the information about the design and mechanics of these tools. Think tanks, for example, fall into this category, as they provide policy-makers with 'basic information about the world and societies they govern, how current policies are working, possible alternatives and their likely costs and consequences' (McGann, Viden, & Rafferty, 2014, p. 31).
In a series of studies on how various emission trading schemes have emerged in environmental policy (Mann & Simons, 2014;Voss & Simons, 2014), Voss and Simons have noted that, just as epistemic communities perpetuate ideas of policy problems and coalition members are occupied with political beliefs, members of instrument constituencies are distinct and stay cohesive due to their unified identification not with a problem definition or political agenda, but rather with their support of a particular policy tool or a specific combination of policy tools.
That is, the members of such constituencies are not necessarily inspired by the same definition of a policy problem or by similar beliefs as are epistemic communities and advocacy coalitions but rather come together to support specific policy solutions or instrument choices. These constituencies are thus 'networks of heterogeneous actors from academia, policy consulting, public policy and administration, business, and civil society, who become entangled as they engage with the articulation, development, implementation and dissemination of a particular technical model of governance' (Voss & Simons, 2014, p. 738).
These actors exist to promote and further develop a particular instrument and are part of conscious groupings that attempt to realize their particular version of that instrument. The practices of such actors 'constitute and are constituted by the instrument' and develop 'a discourse of how the instrument may best be retained, developed, promoted and expanded' (Voss & Simons, 2014). What brings these actors together is the role they play in articulating 'the set of stories, knowledge, practice and tools needed to keep an instrument alive both as model and implemented practice' (Voss & Simons, 2014). Examining how and why this occurs is a subject of inquiry in this special issue.

Agents in the politics streams: advocacy coalitions
Lastly, the 'politics' stream can be thought of as the milieu where advocacy coalitions are most active. The term 'advocacy coalition' is used by students of American policy-making in the context of earlier, less differentiated, subsystem theory to describe the activities of those involved in the political struggle surrounding matching of problem definitions and policy tools (Sabatier & Weible, 2007;Schlager & Blomquist, 1996). These actors are often situated in key decision-making institutions of government and compete to get their choice of problem definitions as well as solutions adopted during the policy process, working within and against epistemic communities and instrument constituencies in order to do so.
Such politically active policy actors are usually more publicly visible than the members of those groups of substantive experts who collaborate in the formulation of policy alternatives or problem definition, and constitute an often 'hidden cluster' of actors. More visible actors of the politics stream can include, as in the case of the US Congress Kingdon examined, 'the president and his high-level appointees, prominent members of the congress, the media and such elections-related actors as political parties and campaigns' (Kingdon, 2011, p. 64), while less visible actors include lobbyists, political party brokers and fixers, and other behind-the-scenes advisors and participants.
As is well known, Sabatier and Jenkins-Smith (1993) first advanced the idea of advocacy coalitions was first advanced during the 1980s as a response to perceived limitations of existing policy process research programmes: the shortcomings of the stages heuristic in establishing a causal theory of the policy process, the poor discussion about the role of scientific knowledge in policy-making, the polarity of the top-down and bottom-up perspectives of policy implementation, the need to consider time horizons of a decade or more when investigating the policy process, and the need to acknowledge the bounded rationality of policy actors. Since then advocacy coalitions have inspired a strong research programme, with many works developing different sets of propositions about advocacy coalition behaviour and activity (see Sabatier, 1987Sabatier, , 1988Sabatier, , 1998Sabatier & Jenkins-Smith, 1993;Sabatier & Weible, 2007;Weible, Sabatier, & McQueen, 2009;. This literature holds that subsystem actors are boundedly rational in that they employ cognitive filters that limit how they perceive information while operating within the subsystem. Actors aggregate and coordinate their actions into coalitions based on shared core policy beliefs and several such coalitions can occupy a subsystem. These beliefs, as well as coalition membership, stay consistent over time. Led by their primary interest in forwarding their beliefs, the realm of coalitions falls distinctly into the political vein of the policy process, as coalitions compete with opposing coalitions to transform their beliefs into policies, tending to amplify the maliciousness of those with opposing beliefs in the process.
The relative success of a coalition in furthering its policies depends on a number of factors, including external factors like natural resource endowments and the nature of policy problems that remain relatively constant over time. Other external factors that have also been found to be important in activity coalition behaviour include public opinion and technology developments. These factors are also more unpredictable. Internal factors include the coalition's own financial resources, level of expertise and number of supporters. Coalition members employ knowledge about what the competing views on important policy problems or solutions are for a 'variety of uses from argumentation with opponents to mobilization of supporters' .
Although often posited as comprising all actors within a policy subsystem, the role of advocacy coalitions in vying to get their preferred problem and solutions chosen in policy decisions can also be thought of, consistent with Kingdon's ideas, as synonymous with activities and actors in the politics stream (Weishaar, Amosb, & Collin, 2015). Exactly what insights from existing coalition theory can be effectively utilized in a streams-type framework remains an outstanding research question and is addressed in some of the articles in this issue.

Overview of the special issue
The overall argument made in this special issue, therefore, is that, following Kingdon's (1984) lead, associating specific groups of subsystem actors with each of the three streams Kingdon (1984) identified provides greater insight and understanding into both agenda-setting and subsequent stages of the policy process than does a more undifferentiated view of policy subsystem composition, membership and activities. Viewing policy-making as composed of the actions of these distinct communities of actors and their interactions during different stages and activities of policy-making, from agenda-setting to policy evaluation, provides a clearer sense of what drives policy-making forward and determines its tempo as well as its content. This idea is distinct from previous authors and policy scholars' work that often conflated specific subsets of subsystem actors with the subsystem itself or that failed to differentiate, as in Kingdon's case, between the very different actors and activities involved in each distinct 'stream' .
Importantly, we do recognize that, as with the three streams themselves, epistemic communities, instrument constituencies and advocacy coalitions can overlap and the same actors can simultaneously belong to at least two of these groups. We also recognize that, in empirical reality, actors' actions are not necessarily confined solely to the policy tasks associated with their respective stream. For instance, epistemic communities or advocacy coalitions can play a role in the formulation of policy solutions even if it is not their primary role. In other words, the above typology of actor types and streams is intended to provide only a general analytical overview of how actors tend to populate the policy subsystem rather than to create rigid and artificial boundaries amongst.
Beyond these general remarks, however, it is clear that, while many of the activities of epistemic communities and advocacy coalitions are reasonably well understood, significant questions remain about some of these activities, about instrument constituencies and about the relationships between these three groups. The articles in this special issue address these points and other issues and will help scholars make sense of instrument constituency as a core concept in public policy research.
The first article of this special issue, written by Arno Simons and Jan-Peter Voß, explains the concept of instrument constituency and sheds new light on what the authors call the 'supply side' of policy-making. For them, an instrument constituency is a set of actors and practices focused on the development and the diffusion of a particular policy instrument. Stressing the role of agency, their theoretical contribution outlines the concept of instrument constituency and creates a dialogue between scholarship on instrument constituencies and existing analytical perspectives in the field of policy research.
In the two articles that follow, Tony Zito and Christopher Weible each explore the relevance of the recent concept of instrument constituency for the existing scholarship on epistemic communities and advocacy coalitions, respectively. They both argue that the concept of an instrument constituency is a useful complement to existing analytical frameworks in policy studies. In other words, as a concept, the instrument constituency does not compete with the well-established concepts of epistemic community and advocacy coalition but rather adds an additional dimension to studies in these areas. From this perspective, we can conclude that all three concepts remain useful to policy scholars interested in mapping the actors directly involved in the policy process.
The next section explores the concept and components of an instrument constituency in more depth. In the first paper, authored by Andrew Sturdy, the role of policy consultants within instrument constituencies is explored. As his analysis suggests, these consultants can play a direct role within instrument constituencies. This is yet another reason to encourage more research on policy consultants, who remained largely understudied as a policy actor, just as instrument coalitions are themselves. Certainly, Sturdy's article suggests that research on policy consultants should engage directly with research on instrument constituencies, and vice versa.
The next three articles provide case studies that illustrate the empirical relevance of the concept of instrument constituency across different policy sectors and geographical regions. Importantly, in order to illustrate the diversity of the empirical issues this concept can help tackle, these three papers focus on truly distinct policy areas. In the first, Anthony Perl discusses the role of instrument constituencies in transportation policy in the US; in the second, Carsten Mann and Nina Amelung explore how citizen panels constitute a policy instrument closely related to a constituency seeking to promote this instrument in Germany; and in the third, Daniel Béland examines how transnational instrument constituencies promoted and pushed the use of a particular tool -the Conditional Cash Transfer or CCT -in social policy circles in Ghana.
This special issue is not intended or expected to be the 'last word' on the concept of an instrument constituency. The concept, which is a recent addition to the public policy literature, deserves much more attention. We hope, however, that this issue will raise the profile of the concept and convince more scholars to refine and test it, and use it in their analytical and empirical research. As suggested here, the concept of instrument constituency does not displace existing concepts and frameworks but rather points our attention towards an important yet understudied set of policy actors that ought to be studied alongside other groups of actors whose activities determine and impact both the timing of policy developments and their content.