[영문]In a previous paper, the reliability of willingness-to-pay (WTP) values was found to be an increasing function of the size of WTP expressed. Here, the results of a qualitative exercise conducted alongside this quantitative study are presented. The results of this exercise suggest that higher WTP values may require more thought from the respondent which, in turn, gives them greater stability. At low levels of WTP, values appear to be taken from a discretionary account, where expenditure is more volatile. Caveats to this result, and suggestions for future research, are considered in the discussion