Do hypothetical and actual marginal willingness to pay differ in choice experiments? Application to the valuation of the environment

In this paper we test the validity of choice experiments with donations far environmental projects. In particular, we test whether or not there are differences in preferences between a hypothetical and an actual choice experiment: our experiments indicate no differences. In addition, internal tests of validity indicate transitive and stable preferences in both experiments, although there are some indications of possible learning effects during the experiment. (C) 2000 Academic Press.