Mix and Match: How Contractual and Relational Conditions Are Combined in Successful Public–Private Partnerships

In explaining public–private partnership (PPP) performance, both contractual and relational conditions play a role. Research has shown that these conditions may complement each other in successful PPPs. However, which specific combinations of conditions and how these combinations may influence PPP performance remains unclear. Building on the ideas of neo-institutional economics, principal–agent theory, relational contracting, and governance theories, this article explores the mix and match of contractual aspects and relational characteristics in successful PPP projects. A fuzzy set qualitative comparative analysis (QCA) of 25 PPP projects in the Netherlands and Flanders (Belgium) was used to test how contractual factors, such as the use of sanctions and risk allocation, and relational conditions, such as trust and conflict management, jointly shape the performance of PPPs. The results show three different combinations of conditions that match with high performing PPPs. These configurations often consist of a mix of contractual and relational conditions, which confirms our initial expectation that these factors complement each other, but a combination of only relational conditions is also present.