Test-Retest Reliability of Choice Experiments in Environmental Valuation

The paper presents the results of the first test-retest study on choice experiments in environmental valuation. In a survey concerning landscape externalities of onshore wind power in central Germany, respondents answered the same five choice sets at two different points in time. Each choice set comprised three alternatives described by five attributes, and the time interval between the test and the retest was eleven months. The analysis takes place at three different levels, investigating choice consistency at the choice task level and repeatability of the latent construct utility at the level of parametric models as well as at the level of willingness-to-pay estimates. At the choice task level we observed 59% identical choices. The parametric analysis shows that the test and retest estimates are not equal, even when we control for scale, that is, differences in the error variance. However, comparing the marginal willingness-to-pay estimates among test and retest reveals only a statistically significant difference for one of the attributes. Overall, this indicates a moderate test-retest reliability taking into account that consistency at the choice task level overlooks the stochastic nature of the process underlying discrete choice experiments.