【正文】 he basis of which criteria do port authorities decide to invest is therefore a central issue for port authorities. We claim that the following simple rule is a guideline for investment appraisal of port cluster managers: benefits for the cluster of an investment should exceed costs for the cluster. Cluster benefits are the sum of all benefits of firms in the cluster, cluster costs are the costs of an investment for firms in the cluster. In most cases costs are incurred because port charges are required for cluster investments. Since costs equal revenues, a high investment level requires high port charges. 4. Cluster governance in the port of Rotterdam In this section we present an empirical case study of the port of Rotterdam. We interviewed 43 port experts in the port of Rotterdam. First, we deal with the importance of cluster governance for the performance of the cluster. In the next four paragraphs, we discuss the empirical results for the four variables that influence the quality of the cluster governance. Sixth, we briefly discuss the role of the port authority in Rotterdam and end with conclusions. The importance of cluster governance in Rotterdam’s seaport cluster These results show that cluster governance is less important than the structure of the cluster and the economic development in general, but more important than national and international policies. The experts were also asked to indicate the relative importance of the four variables of cluster governance, also by ranking them. Trust in Rotterdam’s port cluster Virtually all cluster experts agree with the proposition that trust is important for the quality of the cluster governance, and as discussed above, argue that trust is the most important ‘governance variable’. The cluster experts evaluated the port of Rotterdam and its main petitors, Antwerp and Hamburg, with regard to the presence of trust. Leader firms in Rotterdam’s port cluster Virtually all cluster experts also agree that the presence of leader firms is an important determinant of the quality of cluster governance. The experts evaluate the three peting ports as follows: Rotterdam Antwerp Hamburg presence of leader firms b significantly better than in worst port Antwerp is evaluated the most positive, Hamburg has the lowest score. In general the experts indicate that all three ports do score relatively good with regard to leader firms. Intermediaries in Rotterdam’s port cluster With regard to intermediaries, a significant majority of the experts agree with the presumed positive effect of intermediaries on cluster governance, but nine out of the 43 disagree. Solutions for CAP’s in Rotterdam’s port cluster Finally, we discuss the quality of solutions for collective action problems. Out of the five proposed CAP’s in seaports, the cluster experts judged four relevant： Issue Collective action problem Relevant Not relevant Training and education 38a 3 Marketing and promotion 37 a 4 Hinterland access 37 a 4 Innovation 29 a 12 Internationalism 13 28 a a significant majority The role of the port authority in Rotterdam The Rotterdam municipal port authority (RMPM) is a public landlord port. The galvanization formally is a part of the municipality Rotterdam but operates to a large extent autonomous. Currently, a modification of the institutional structure, t