Social discount rate: spaces for agreement

We study the problem of aggregating discounted utility preferences into a social discounted utility preference model. We use an axiom capturing a social responsibility of individuals’ attitudes to time, called consensus Pareto. We show that this axiom can provide consistent foundations for welfare judgments. Moreover, in conjunction with the standard axioms of anonymity and continuity, consensus Pareto can help adjudicate some fundamental issues related to the choice of the social discount rate: the society selects the rate through a generalized median voter scheme.

Positive Social Time Preference

Recent debates have made it clear that the choice of a social discount rate has enormous consequences for the amount of carbon abatement that will be recommended. The social discount rate determines how future costs are to be compared to present costs. Philosophers have been almost unanimous in endorsing the view that the only acceptable social rate of time preference is zero, a view that, taken literally, has either absurd or extremely radical implications. The first goal of this chapter is to show that the standard arguments against temporal preference are much less persuasive than they are usually taken to be. The second goal is to explore three different avenues of argument that could be adopted in order to show that temporal discounting of welfare may be permissible. The chapter concludes with a suggestion for how deontologists could accept a pure time preference derived from the current global death rate.

Decision Making Under Model Uncertainty: Fréchet–Wasserstein Mean Preferences

This paper contributes to the literature on decision making under multiple probability models by studying a class of variational preferences. These preferences are defined in terms of Fréchet mean utility functionals, which are based on the Wasserstein metric in the space of probability models. In order to produce a measure that is the “closest” to all probability models in the given set, we find the barycenter of the set. We derive explicit expressions for the Fréchet–Wasserstein mean utility functionals and show that they can be expressed in terms of an expansion that provides a tractable link between risk aversion and ambiguity aversion. The proposed utility functionals are illustrated in terms of two applications. The first application allows us to define the social discount rate under model uncertainty. In the second application, the functionals are used in risk securitization. The barycenter in this case can be interpreted as the model that maximizes the probability that different decision makers will agree on, which could be useful for designing and pricing a catastrophe bond. This paper was accepted by Manel Baucells, decision analysis.

Discounting under Risk

The debate on the economics of climate change has focused primarily on the choice of the social discount rate, which plays a key role in determining the desirability of climate policies given the long-term impacts of climate damages. Discounted utilitarianism and the Ramsey Rule dominate the debate on discounting. The chapter examines the appropriateness of the utilitarian framework for evaluating public policies. More specifically, it focuses on the risky dimension of climate change, and on the failure of utilitarianism in expressing both concerns for the distribution of risks across the population and concerns for the occurrence of catastrophic outcomes. The chapter shows how a shift to the prioritarian paradigm is able to capture those types of concerns, and briefly sketches the main implications for the choice of the social discount rate.

Discounting and the Green Transition: District Heating in Denmark

Taking Aalborg as the basis for a case study, we consider the discount rates, annuity rates and costs of capital that were used in recent socio-economic and financial Net Present Value (NPV) analyses of a proposed geothermal district heating plant. While the core NPV analysis applied a real social discount rate of 4 percent, in keeping with Danish government guidance, emissions and electricity prices were based on costs of capital that differed from this rate, as did the annuity rate applied in the financial analysis of the project. While the different rates are carefully justified in each setting, we question whether there is consistency in the approach taken to intergenerational welfare across different steps of the analysis. The use of high corporate rates in some contexts potentially makes it more difficult for Green Transition projects to meet the legal requirement of being evaluated as socio-economically optimal.

The Entrepreneurial Social Discount Rate: Risk Premium and Loss Aversion in New Ventures

We derive a mathematical extension of the social discount rate (SDR) in such a way that we can valuate intergenerational startups financed with personal and government funds at the aggregate level. The results imply that the precise determination of the SDR can change the financial priority of investment. Therefore, we recommend government officials to include factors of economic growth (wealth effect), intergenerational prevention (precautionary effect), loss aversion, and the specific risk of the business in the valuation of new ventures and in the estimation of the social discount rate to be more representative of the social utility. Our contribution lies in including a risk premium from the firm’s average non-systematic risk and the loss aversion of a representative investor in estimating the SDR.

Discounting for Energy Transition Policies—Estimation of the Social Discount Rate for Poland

The transition of the energy system in Poland has a long time horizon and demands a substantial investment effort supported by proper economic evaluation. It requires a precise Social Discount Rate (SDR) estimation as discounting makes the present value of long-term effects extremely sensitive to the discount rate level. However, Polish policymakers have little information on SDR: the predominant practice applies a priori fixed 5% discount rate, while studies devoted only to Poland are quite rare. To eliminate this research gap, our paper aims at estimating SDR for Poland, applicable in energy transition policies. We derive SDR for three datasets varying in length, twofold: using market rates via Consumption Rate of Interest (CRI) and Social Opportunity Cost (SOC) of capital, and prescriptive Ramsey and Gollier approaches based on Social Welfare Function (SWF). The results indicate that the rates based on CRI and SOC deviate substantially with changing data timeframes and market conditions, while prescriptive methods show much higher time stability. Due to long-term planning horizons for energy policies, we argue for adopting, as SDR in Poland, the longest dataset’s Ramsey-based rate of 4.72% which can be reduced to 4.39% by Gollier’s precautionary term (reflecting the uncertainty over future consumption growth), which are our main findings.