Complex societal or environmental problems require fast and substantial socio-technical transitions. For instance, in the case of climate change, these transitions need to take place in the energy, transport and several industry sectors. To induce and accelerate such transitions, numerous policy interventions are required, which interact with each other in policy mixes. While several conceptual studies on policy mixes have been published recently, there is very little empirical research apart from single case or small-n studies. It has been prominently argued that the debate about policy mixes has reached an impasse partly due to this lack of empirical work. This paper addresses this gap by providing a first analysis of the temporal dynamics of complex policy mixes. To do so, we develop a conceptualization and measurement of policy mix balance across instrument types as well as policy mix design features (in the form of intensity as a general and technology specificity as a technology-focused design feature). This allows us to answer the question how temporal dynamics of policy mixes differ between countries regarding their balance and design features. Our measurement approach is developed bottom-up, i.e., policies are assessed individually and then aggregated systematically at the policy mix level. This enables overcoming the 'dependent variable problem in the study of policy change', i.e., the problem of measuring policy output. More specifically, we develop a comparative dataset of 522 renewable energy policies in nine OECD countries. Our analysis shows that countries' policy mix dynamics vary strongly regarding some variables (e.g., technology specificity) but less regarding others (e.g., balance). As a validity check, we also test the effects of these mix dynamics on policy outcome in the form of renewable energy technology diffusion. We reflect our findings in light of the theoretical debates around policy mixes and policy design and discuss how our results provoke an agenda for the new generation of research on policy mixes. We specifically discuss avenues for future research with a particular focus on the 'politics of policy mixes'.
