The nominal interest rate also affected delay discounting (Experiment 2).
Different combinations of inflation and nominal interest rates that yielded the same real interest rate also had some effect on delay discounting (Experiment 3).
The results of this study have implications for the relationship between individual discounting and market discounting.
The present results, however, show that individual subjective discounting is also affected by macroeconomic factors (interest and inflation rates).
Thus, the results of delay discounting experiments from different countries and times should not be compared lightly; neglecting macroeconomic factors may yield misleading conclusions regarding the behavior of participants.
Moreover, the term structure of subjective discounting is different from that of market discounting.
Macroeconomic factors only affect some parameters and outcomes in delay discounting experiments.
In the experiments conducted for this study, delay length and the indirect relation between the rewards provided and actual Japanese yen payments may limit the degree to which the delay discounting behavior observed can be generalized.
The short delay lengths and the indirect relation between delayed rewards and incentives may have failed to elicit the same participant time-preferences observed in real-world delay discounting.
Participants in delay discounting experiments might not usually pay attention to economic factors such as interest and inflation rates.
Most delay discounting studies have used hypothetical rewards.