Economic valuation of the envi- structuring the empirical model, or adding ronment is disputed, in part, due to the number auxiliary hypotheses. The presumption is of anomalies. Reactions to these anomalies have that consistent preferences are there just included adding new auxiliary hypotheses to the to be uncovered. Thus, errors are “mea- core model or dismissing the whole undertaking. surement This paper takes a third route, and uses observa- biases” to be corrected by retions made in valuation studies to improve choice fined methods (Mitchell and Carson theory. The paper covers the information prob- 1989) . Certainly, many studies can be critlem, the issue of preference formation, and under- icized for being of low quality. Still, the lines the role of the social sphere in defining what development of concepts like “starting becomes individually rational. While the findings point bias,” “posit ion bias,” “question ormay not simplify theory, they may help us be- der bias,” “yea-saying,” “protest bids,” come more realistic and to understand errors pro- and “part-whole bias” all seem very ad duced by illegitimate simplifications.