Discount function

A Discount Function is used in economic models to describe the weights placed on rewards received at different points in time. For example, (if time is discrete and utility is time-separable) if the discount function is $f(t)$ then total utility is given by: $U(\{c_{t}\}_{t=0}^{\infty })=\sum _{t=0}^{\infty }{f(t)*u(c_{t})}$.

For a comprehensive review, see: Shane Frederick & George Loewenstein & Ted O'Donoghue, 2002. "Time Discounting and Time Preference: A Critical Review," Journal of Economic Literature, vol. 40(2), pages 351-401, June.