There is a perception that infrastructure developed and managed through Public-Private Partnerships (PPPs) outperforms infrastructure developed and managed traditionally. This perception is a core motivation for policymakers and infrastructure planners to pursue PPPs. However, the evidence for such a performance advantage is scant in the academic literature, due to a dominance of single case studies, a lack of good benchmarks or 'counterfactual' situations, and a scarcity of actual project performance data. These reasons suggest we need more comparative studies which analyze materialized performance. In this chapter, we begin with a discussion of existing comparative studies on cost performance, time performance, and service quality performance, thereby contextualizing the empirical chapters featured in the remainder of this edited volume. We also argue for a quasi-experimental design for the assessment of the performance advantage of PPPs, which is the approach taken by the empirical chapters in this book.