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Why uncertainty matters: discounting under intertemporal risk aversion and ambiguity

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  • Christian Traeger

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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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    Cited by:

    1. van den Bijgaart, Inge & Gerlagh, Reyer & Liski, Matti, 2016. "A simple formula for the social cost of carbon," Journal of Environmental Economics and Management, Elsevier, vol. 77(C), pages 75-94.
    2. Crost, Benjamin & Traeger, Christian P., 2013. "Optimal climate policy: Uncertainty versus Monte Carlo," Economics Letters, Elsevier, vol. 120(3), pages 552-558.
    3. Lemoine, Derek & Traeger, Christian P., 2016. "Ambiguous tipping points," Journal of Economic Behavior & Organization, Elsevier, vol. 132(PB), pages 5-18.
    4. Svenja Hector, 2013. "Accounting for Different Uncertainties: Implications for Climate Investments?," Working Papers 2013.107, Fondazione Eni Enrico Mattei.
    5. Simon Quemin, 2016. "Intertemporal abatement decisions under ambiguity aversion in a cap and trade," Working Papers 1604, Chaire Economie du climat.
    6. Chambers, Robert G. & Melkonyan, Tigran, 2017. "Ambiguity, reasoned determination, and climate-change policy," Journal of Environmental Economics and Management, Elsevier, vol. 81(C), pages 74-92.
    7. Freeman, Mark C. & Groom, Ben, 2016. "How certain are we about the certainty-equivalent long term social discount rate?," Journal of Environmental Economics and Management, Elsevier, vol. 79(C), pages 152-168.
    8. Iverson, Terrence, 2013. "Minimax regret discounting," Journal of Environmental Economics and Management, Elsevier, vol. 66(3), pages 598-608.
    9. Jensen, Svenn & Traeger, Christian P., 2014. "Optimal climate change mitigation under long-term growth uncertainty: Stochastic integrated assessment and analytic findings," European Economic Review, Elsevier, vol. 69(C), pages 104-125.
    10. Yongyang Cai & Kenneth L. Judd & Thomas S. Lontzek, 2013. "The Social Cost of Stochastic and Irreversible Climate Change," NBER Working Papers 18704, National Bureau of Economic Research, Inc.
    11. Christian Traeger, 2014. "A 4-Stated DICE: Quantitatively Addressing Uncertainty Effects in Climate Change," Environmental & Resource Economics, Springer;European Association of Environmental and Resource Economists, vol. 59(1), pages 1-37, September.
    12. Iverson , Terrence & Karp, Larry, 2017. "Carbon taxes and climate commitment with non-constant time preference," Department of Agricultural & Resource Economics, UC Berkeley, Working Paper Series qt3hw6s14v, Department of Agricultural & Resource Economics, UC Berkeley.
    13. Luciano I. Castro & Zhiwei Liu & Nicholas C. Yannelis, 2017. "Ambiguous implementation: the partition model," Economic Theory, Springer;Society for the Advancement of Economic Theory (SAET), vol. 63(1), pages 233-261, January.
    14. Svenja Hector(), "undated". "Accounting for Different Uncertainties: Implications for Climate Investments?," Working Papers ETH-RC-13-007, ETH Zurich, Chair of Systems Design.
    15. Fleurbaey, Marc & Zuber, Stéphane, 2015. "Discounting, beyond utilitarianism," Economics - The Open-Access, Open-Assessment E-Journal, Kiel Institute for the World Economy (IfW), vol. 9, pages 1-52.
    16. Hector, Svenja, 2015. "Extending the Ramsey Equation further: Discounting under Mutually Utility Independent and Recursive Preferences," Annual Conference 2015 (Muenster): Economic Development - Theory and Policy 113061, Verein für Socialpolitik / German Economic Association.
    17. Hiroaki Sakamoto & Ken-Ichi Akao, "undated". "A theory of disasters and long-run growth," Discussion papers e-17-014, Graduate School of Economics , Kyoto University.
    18. van den Bijgaart, Inge, 2016. "Essays in environmental economics and policy," Other publications TiSEM 298bee2a-cb08-4173-9fe1-8, Tilburg University, School of Economics and Management.
    19. Howard, Peter H. & Derek, Sylvan, 2016. "The Wisdom of the Economic Crowd: Calibrating Integrated Assessment Models Using Consensus," 2016 Annual Meeting, July 31-August 2, 2016, Boston, Massachusetts 235639, Agricultural and Applied Economics Association.
    20. Larry S. Karp, 2012. "Provision of a Public Good with Altruistic Overlapping Generations and Many Tribes," CESifo Working Paper Series 3895, CESifo Group Munich.

    More about this item

    Keywords

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

    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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