Insensitivity to payment schedule, wherein respondents do not adequate
ly differentiate between a one-time payment and a series of payments m
ay be an important but often overlooked factor in the design, interpre
tation, and use of contingent valuation studies. Several contingent va
luation experiments involving a familiar private good and a less famil
iar environmental commodity indicate that although respondents disting
uished between lump sum and periodic payment schedules, implicit disco
unt rates were very high, suggesting that sensitivity to payment sched
ule is an important subject for further study.