Resolving a complex policy problem often requires a mix of policy instruments and thus the identification of the most promising instrument combination. However, the relevant terminology of instrument interactions in a policy mix has not been standardized, hindering a straightforward identification of superior instrument combinations. To address this challenge, the chapter defines the terminology necessary for detecting three different possible policy instrument interactions—namely synergistic, counter-productive, and additive effects. It identifies two approaches to analyzing instrument mix effects: the “effect-based” and the “effort-based” methods. It then discusses the practical advantages and limitations of each approach and elaborates on key methodological issues that policy scholars and practitioners face at each step of developing a new policy mix. 

Disproportionate policy response is understood to be a lack of ‘fit’ or balance between the costs of a public policy and the benefits derived from this policy, and between policy ends and means. The study of this phenomenon and its two anchor concepts, namely, policy over- and underreaction, has been inspired by the insight that inefficiencies in the allocation of attention in policymaking leads policymakers to react disproportionately to information. This theory of information processing appears to be broadly accepted and has generated a large body of research on agenda setting. However, little attention has been devoted to actual policy over- and underreaction and how it affects the public. The latest developments are conceptual in nature and include a conceptualization and dimensionalization of policy over- and underreaction, as well as an early-stage development of a preference-driven approach to disproportionate policy response. These issues are fundamental to developing understanding of the formulation, implementation, and evaluation of disproportionate policy response. They are also valuable to those who want to better understand the processes through which policy over- and underreaction occur and are of considerable interest to practitioners who want to understand how to manage disproportionate policy responses more effectively.

Although disproportionate policy response poses methodological challenges because it is time-bound, context-sensitive and has a problematic counterfactual (i.e., proportionate policy response), it deserves academic attention. This is because the insight of the punctuated equilibrium theory—that policy responses oscillate between periods of underreaction to the flow of information coming from the environment into the system and overreaction due to disproportionate information processing—implies that policy oscillation is the norm rather than the rarity. To probe research questions related to the topic at hand, disproportionate policy response can be measured as individuals’ perceptions of what they think about the proportionality of policy. Alternatively, scholars may employ vignette survey experiments, sophisticated cost-benefit analysis and a comparison of policy outcomes with (national or international) standards developed by experts. Scholars may also undertake experimental manipulation using risk unfolding over time, combined with varying types of warnings.

The study of disproportionate policy response is a gateway to some of the most significant aspects of public policy. Global and domestic threats coupled with relatively skeptical publics about politicians and political institutions and rising negativity and populism in democratic politics imply that policy overshooting is increasingly required for the public to perceive policy action as sufficient and politicians as competent, at least in the short term. Not only has disproportionate policy response been a focal point for political actors seeking decisive and swift policy change in times of real or manufactured crisis or no change at all, but such action has time and time again also made a dramatic impact upon the direction and the character of policy and politics. Classic examples are the U.S. response to 9/11 and the federal response to Hurricane Katrina. So far the literature on policy change has not responded to the emergence of the stream of research aimed at fully understanding the complex phenomenon of disproportionate policy response, but a robust research agenda awaits those answering this article’s call for action.