Introduction -- Policy Research in the Face of Complexity -- Actor-Centered Institutionalism -- Actors -- Actor Constellations -- Unilateral Action in Anarchic Fields and Minimal Institutions -- Negotiated Agreements -- Decisions by Majority Vote -- Hierarchical Direction -- Varieties of the Negotiating State -- A Game-Theoretical Interpretation of Inflation and Unemployment in Western Europe -- Efficient Self-Coordination in Policy Networks-A Simulation Study