Stated preference valuation is a family of techniques which use individual respondents' statements about their preferences to estimate change in utility associated with a proposed increase in quality or quantity of an ecosystem service or bundle of services. Respondents are presented with one or more hypothetical policy or project scenarios that lead to a specified environmental change compared to a baseline situation. The answers respondents give, in the form of monetary amounts, ratings, or other indications of preference, are scaled following an appropriate model of preferences to yield a measure of value of the proposed ecosystem service change. This value is often monetary expressed as peoples willingness to pay. Stated preferences are often elicited through surveys (typically web, phone, mail or in-person) that use questionnaires following strict guidelines.