A study analysing the performance of research clusters in eight northern European states has confirmed that the largest ones are most effective. The NGP Excellence Cluster—a project between the Nordic countries, Germany and Poland that was initiated by Denmark—compared the track record of 140 clusters, looking at 16 of them in detail. Its final report offers eight recommendations for clusters, including the need for long-term, flexible support and the requirement for strong monitoring and evaluation of results and impacts.