PPP專案財務評估之方法論修正與實證分析

Abstract

現行PPP專案民間方投資可行性評估，主要方式為建置財務模型進行定量分析，其評估方法多使用依據傳統資本預算理論訂定之財務指標如淨現值，惟該指標將受折現率選用之高低而有不同評估結果，且用於決定折現率之WACC公式本身，亦存有資本結構比例假設及Ke難以公允訂定等問題，本研究將梳理傳統資本運算理論，並搭配焚化爐、再生水及路燈等基礎建設案例進行實證分析，分析資本結構假設變化以及興建期折現率擇定對於專案評估的影響，並歸納整理前述案例中投資者關心之議題(既在意的風險)，彙整以PPP專案風險特性訂定之Ke區間，以提出評估方法論之修正。 以採用動態WACC，興建期折現率採用物價調整率及以PPP專案風險特性訂定Ke之修正評估方法論進行實證分析之結果顯示修正後的評估方法論可降低樂觀偏誤。

The current feasibility assessment of private sector investment in PPP projects mainly relies on building financial models for quantitative analysis. The evaluation methods often utilize traditional capital budgeting theory to establish financial indicators such as Net Present Value (NPV). However, the NPV is sensitive to the selection of the discount rate, leading to varying evaluation results. Moreover, the determination of the Weighted Average Cost of Capital (WACC) formula itself faces challenges due to assumptions about capital structure proportions and difficulties in setting a fair Ke (required rate of return).

In this study, we will review the traditional capital budgeting theory and conduct empirical analyses with case studies on infrastructure projects such as incinerators, recycled water facilities, and street lighting. We will examine the impact of changes in capital structure assumptions and the selection of the discount rate during the construction period on project evaluations. Additionally, we will identify the issues that investors are concerned about (i.e., relevant risks) and consolidate the Ke range based on the characteristics of PPP project risks, proposing a modified evaluation methodology.

The proposed approach will adopt dynamic WACC and use the inflation rate as the discount rate during the construction period, while considering the revised Ke range based on PPP project risk characteristics. The results of the empirical analysis demonstrate that the modified evaluation methodology can reduce optimistic biases in the assessments.