Four Score and Seven Years from Now: The Date/Delay Effect in Temporal Discounting

We describe a new anomaly in intertemporal choice---the "date/delay effect": discount rates that are imputed when time is described using calendar dates (e.g., on October 17) are markedly lower than those revealed when future outcomes are described in terms of the corresponding delay (e.g., in six months). Date descriptions not only reduce discount rates, but also affect the implied shape of the discount function: When inferred from intertemporal choices between options referenced by calendar dates, the discount function appears markedly less hyperbolic. We discuss potential psychological bases of the date/delay effect, its implications, and other modes of temporal reference.