What’s it worth? Exploring value uncertainty using interval questions in Contingent Valuation

In this paper we explore the idea that people only know the value they place on a given environmental change as a range, rather than as a singleton. We use the payment ladder design of contingent valuation, and take as a case study the value of coastal water quality improvements in Scotland. Kaplan-Meier survival curves, Tobit analysis and a modified Turnbull algorithm are used to explore the data. We find that most people state their values as a range, and investigate empirically the determinants of this range. The paper concludes with some thoughts concerning possible links between value ranges, context-dependence and uncertainty.