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Why uncertainty matters: discounting under intertemporal risk aversion and ambiguity

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  • Christian Traeger

Abstract

Uncertainty has an almost negligible impact on project value in the standard economic model. I show that a comprehensive evaluation of uncertainty and uncertainty attitude changes this picture fundamentally. The illustration of this result relies on the discount rate, which is the crucial determinant in balancing immediate costs against future benefits, and the single most important determinant of optimal mitigation policies in the integrated assessment of climate change. First, the paper removes an implicit assumption of (intertemporal or intrinsic) risk neutrality from the standard economic model. Second, the paper introduces aversion to non-risk uncertainty (ambiguity). I show a close formal similarity between the model of intertemporal risk aversion, which is a reformulation of the widespread Epstein–Zin–Weil model, and a recent model of smooth ambiguity aversion. I merge the models, achieving a threefold disentanglement between risk aversion, ambiguity aversion, and the propensity to smooth consumption over time. Copyright Springer-Verlag Berlin Heidelberg 2014

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  • Christian Traeger, 2014. "Why uncertainty matters: discounting under intertemporal risk aversion and ambiguity," Economic Theory, Springer;Society for the Advancement of Economic Theory (SAET), vol. 56(3), pages 627-664, August.
  • Handle: RePEc:spr:joecth:v:56:y:2014:i:3:p:627-664
    DOI: 10.1007/s00199-014-0800-8
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    More about this item

    Keywords

    Climate change; Discounting; Risk aversion; Ambiguity; Cost-benefit analysis; Intertemporal substitutability; Uncertainty; D61; D81; D90; H43; Q00; Q54;
    All these keywords.

    JEL classification:

    • D61 - Microeconomics - - Welfare Economics - - - Allocative Efficiency; Cost-Benefit Analysis
    • D81 - Microeconomics - - Information, Knowledge, and Uncertainty - - - Criteria for Decision-Making under Risk and Uncertainty
    • D90 - Microeconomics - - Micro-Based Behavioral Economics - - - General
    • H43 - Public Economics - - Publicly Provided Goods - - - Project Evaluation; Social Discount Rate
    • Q00 - Agricultural and Natural Resource Economics; Environmental and Ecological Economics - - General - - - General
    • Q54 - Agricultural and Natural Resource Economics; Environmental and Ecological Economics - - Environmental Economics - - - Climate; Natural Disasters and their Management; Global Warming

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