Abstract
This study paid attention to the difference of WTP (Willingness to Pay) by the difference of payment unit in CVM (Contingent Valuation Method), and measured the discount ratio which was based on difference between the Annual WTP and the Life WTP, by applying the discount function which was discussed well in behavioral economics as psychological approach. Then, we discussed the time preference of people and the validity of current discount ratio (4% annually) which is being used in evaluation of public works in Japan. This result pointed out the problem that the current discount ratio may have the possibility of over-estimation and/or under-estimation of total benefit which depend on conditions.
