Cluster policy in an evolutionary world? Rationales, instruments and policy learning

Despite the popularity of the concept of "cluster of innovation" and its widespread use in policy, surprisingly little is understood regarding the nature of these interventions and their impact. Paradoxically, increasing demands for evaluation and evidence-based policy are being made at a time when increased policy complexity is challenging these very efforts towards policy learning. Cluster policy is an extreme example of this, given the lack of clear rationales, and the multidimensional and multi-instrument nature of the intervention. This chapter aims to shed some light into this policy complexity.