One of the most interesting and current debates in financial economics concerns the behavior of active shareholders and their impact on firm performance. Active owners can be viewed as those that stay and try to increase firm value, whereas passive owners rely more on retrospective information and vote with their feet (Tirole, 2006). In our research project, we will examine costs and benefits that arise from having controlling shareholders and other large shareholders in publicly traded firms in four separate sub projects. The first project studies the performance of founder- and descendant-controlled firms in different institutional settings in Europe. The second project deals with the impact of different types of activist owners on the policy of Western European firms. The third project studies active owners in Finnish listed firms. Finally, the fourth project investigates how different types of investors react to new public information. Taken together, the goal of our research program is to empirically explore the implications of various forms of shareholder activity on firms to significantly enhance the understanding of financial markets and their development.