Nearly all discussions about the appropriate consumption discount rate for climate-change policy evaluation assume that a single discount rate concept applies. We argue that two distinct concepts and associated rates apply. We distinguish a social-welfare-equivalent discount rate appropriate for...

The view that intergenerational distributive justice and efficiency should be treated separately is familiar, yet controversial. This article elaborates the often-implicit justifications for separate treatment and provides a more express statement of how and when such treatment is appropriate....

We model welfare-maximizing policy in an infinite-horizon setting when the probability of a tipping point, the welfare change due to a tipping point, and knowledge about a tipping point's trigger all depend on the policy path. Analytic results demonstrate how optimal policy depends on the...

Policymaking for posterity involves current decisions with distant consequences. Contrary to conventional prescriptions, we conclude that the greater wealth of future generations may strengthen the case for preserving environmental amenities; lower discount rates should be applied to the far...

Optimal policy rules--including those regarding income taxation, commodity taxation, public goods, and externalities--are typically derived in models with homogeneous preferences. This article reconsiders many central results for the case in which preferences for commodities, public goods, and...

The growing application of cost-effectiveness (CE) analysis and controversies about its methods has led to a need to explore its welfare economic foundations. Examination of its welfare theoretic foundations can provide a rationale for selecting specific standards for the application of CE...

Experimentally elicited discount rates are frequently higher than what one would infer from market interest rates and seem unreasonable for economic decision-making. Such high rates have often been attributed to present bias and hyperbolic discounting. A commonly recognized bias of standard...

This essay revisits the question of instrument choice for the regulation of externalities in the context of climate change. The central point is that the Pigouvian prescription to equate marginal control costs with the expected marginal benefits of damage reduction should guide the design of...