Figure 1.

Individual differences in discount functions. (A) Future value of $1 received today with exponential discount function at different discount rates r, that is, the value of an amount received after a given delay that is equivalent to $1 received today. This is the amount at which a decision-maker with a given discount function is indifferent between receiving this amount at a given delay, and $1 received today. (B) Discounted value of $1 received at a given delay, assuming an exponential discount function with discount rate r, that is, the value to the decision-maker today of $1 received at a given delay. (C) Discounted value of $1 received at a given delay, assuming different discount functions (exponential function with discount rate r = 0.2, hyperbolic discount function with discount rate k = 0.25, quasi-hyperbolic discount function with parameters β = 0.8, δ = 0.9).