5. Conclusion and policy implications
Our findings are related to the optimal method of government participation to support private investment with social spillovers. In this paper, we developed the model with the idea in mind of a climate change project. Precisely, the project involves two stages that are connected through an externality parameter (investment and management), final payoffs are uncertain, and society receives a benefit from its termination. For instance, there is an initial investment in technologies/plants that can facilitate subsequent energy cost savings or adaptation practices whose payoffs are uncertain but also beneficial for society.
As a major finding, we show that in such contexts where contracts based on contractible outcomes are often not feasible due to the high level of future uncertainty, PPPs may represent an interesting option to eliminate the presence of contract incompleteness, enhance performances and overcome operational constraints (Tompkins and Eakin, 2012; Agrawala and Fankhauser, 2008). Several academic and institutional documents exist that suggest the use of PPPs in the energy, forestry, agriculture and tourist sectors to enhance innovative and/or clean investments (Knoot and Rickenbach, 2014; Sturla, 2012; Wong et al., 2012; Spielman et al., 2010; Brown, 2001; Sperling, 2001). With this paper, we demonstrate if and why PPPs may improve welfare within such contexts. In fact, we are able to show that PPPs as opposed to public subsidies lead to higher levels of final outcomes (investment and effort) thanks to direct government involvement in the decisionmaking process that places more emphasis on the social returns of the project in the final outcomes. This result is even more relevant in a context of budget constraints (high level of λ). Indeed, if governments are not able to provide relevant public subsidies, they can eliminate the problem by using a PPP that, as a public policy, is more cost efficient.