  We prove an analogue of Weitzman's (1998) famous result that an exponential
discounter who is uncertain of the appropriate exponential discount rate should
discount the far-distant future using the lowest (i.e., most patient) of the
possible discount rates. Our analogous result applies to a hyperbolic
discounter who is uncertain about the appropriate hyperbolic discount rate. In
this case, the far-distant future should be discounted using the
probability-weighted harmonic mean of the possible hyperbolic discount rates.
