Despite the growing body of literature evaluating cluster policies, it still remains difficult to establish conclusively their structural effects on regional innovation networks. Focusing on the French cluster policy during the period 2005-2010, this study aims at evaluating how cluster policies influence the structure of local innovation networks following network topologies that may be beneficial for regional innovation. Based on a panel data of four periods and 94 NUTS3 French regions, we estimate spatial Durbin models, allowing us to identify direct, indirect and total effects of cluster policies. The results suggest that cluster policies can result in both positive and negative total effects on the structure of local innovation networks depending on regions' technological specialisation. Beyond the heterogeneous effects, the results also highlight that cluster policies may lead to a regional competition for the strengthening of innovation networks. This finding echoed previous research pointing out the possible 'beggar-thy-neighbour' effects of cluster policies.

Whereas most collaboration-based innovation policies aim at fostering efficient ecosystems of innovation, evaluations of the behavioral impact of such policies remain few and far between. Relying on external-to-the-policy network data to build a counterfactual approach, this article addresses three main evaluation issues: do cluster policies make firms more collaborative? Do they encourage local ties? Do they induce network additionality? Focusing on French data, our results suggest that cluster policies may have difficulty in increasing the centrality of agents within knowledge networks.

Whereas most collaboration-based innovation policies aim at fostering efficient ecosystems of innovation, evaluations of the behavioural impact of such policies remain few and far between. Relying on external-to-thepolicy network data to build a counterfactual approach, this paper addresses three main evaluation issues: do cluster policies make firms more collaborative? Do they encourage local ties? Do they induce network additionality? Focusing on French data, our results suggest that cluster policies may lack effectiveness in tackling network failures.

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