Hyperbolic Discounting is Rational: Valuing the Far Future with Uncertain Discount Rates
J. Doyne Farmer
Santa Fe Institute; LUISS Guido Carli University
Yale University - Cowles Foundation
August 13, 2009
Cowles Foundation Discussion Paper No. 1719
Conventional economics supposes that agents value the present vs. the future using an exponential discounting function. In contrast, experiments with animals and humans suggest that agents are better described as hyperbolic discounters, whose discount function decays much more slowly at large times, as a power law. This is generally regarded as being time inconsistent or irrational. We show that when agents cannot be sure of their own future one-period discount rates, then hyperbolic discounting can become rational and exponential discounting irrational. This has important implications for environmental economics, as it implies a much larger weight for the far future.
Number of Pages in PDF File: 18
Keywords: Hyperbolic discounting, Environment, Time consistent, Exponential discounting, Geometric random walk, Term structure of interest rates
JEL Classification: D91, G12
Date posted: August 15, 2009
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