The social discount rate (SDR) reflects the social conception of how future benefits and costs are compared to present ones. It is used in the economic analysis of project investments to discount economic costs and benefits, reflecting the opportunity cost of capital from an inter-temporal perspective for society. European Commission guidelines recommend an SDR of 5% for major projects in Cohesion countries and 3% for the other Member States. However, states can establish a different benchmark for the SDR if: “i) justification is provided for this reference on the basis of an economic growth forecast and other parameters; ii) their consistent application is ensured across similar projects in the same country, region or sector.” (Guide to Cost-Benefit Analysis of Investment Projects 2014, p. 55). The aim of this dissertation is to investigate the adoption of SDR in infrastructure appraisal, addressing some/all of the following questions:

• Which are the different options/formulas for calculating the SDR?
• Which are the main factors influencing the SDR value?
• How are differences in SDR values justified?
• Which are the values commonly used as SDR?

This dissertation will be co-supervised by Dr Benito Mignacca from the University of Cassino and Southern Lazio (Italy). Dr Mignacca is a Research Fellow in Economic and Managerial Engineering. He obtained his PhD at the University of Leeds (UK) in 2021, where he received the 2021 School of Civil Engineering Postgraduate Award in recognition of his academic performance. Before joining the University of Cassino and Southern Lazio in 2022, he worked as Research Fellow in “Energy Storage Economics and Finance” at the University of Leeds, where he supervised several Master’s students for their dissertations. He co-authored >10 peer-reviewed publications about large infrastructure, and he attracted >60000€ in research funding related to large infrastructure.