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The paper explores the consequences of limited substitutability in welfare between environmental and produced goods for long-term evaluation. I show how the magnitude and time development of optimal social discount rates depend on the substitutability between the different classes of goods. The notions of weak and strong sustainability are translated into the degree of substitutability. I show that a strong notion of sustainability results in lower weights given to long-run service and consumption streams compared to a weak notion of sustainability.

We study the problem of resolving conflicting discount rates via a social choice approach. We introduce several axioms, seeking to capture the tension between allowing for intergenerational comparisons of utility, and imposing intergenerational fairness. Depending on which axioms are judged appropriate, we are led to one of several conclusions: a utilitarian, maxmin, or a multi‐utilitarian rule, whereby a utility stream is judged by the worst in a set of utilitarian weighting schemes across discount rates. [ABSTRACT FROM AUTHOR]

This paper provides two illustrative examples on how a choice of social welfare criterion (conditional vs. unconditional utility) can generate different welfare implications. The first example is based on the standard linear-quadratic permanent income model, and the other example uses a simple two-country DSGE model under autarky and under complete markets. When the conditional welfare criterion is used—with the social discount factor set at the private discount factor—we obtain the well-known results that the government should not intervene when there are no market imperfections and that complete markets generate risk sharing gains over autarky. In contrast, using an unconditional welfare criterion—which effectively implies that the social discount factor is set to unity—can generate unconventional welfare results. [ABSTRACT FROM AUTHOR]

Abstract: The paper shows how limited substitutability in consumption between different classes of goods affects the magnitude and time development of social discount rates. It decomposes the discount rates into an absolute growth and a relative growth or substitutability effect. The paper relates between-good and intertemporal substitutability to the notions of weak and strong sustainability. It analyzes under which circumstances low as opposed to high between-good substitutability increases the weights given to long-run environmental services. [Copyright &y& Elsevier]