The increasing use of internet surveys for stated preference studies raises questions about the effect of the survey mode on welfare estimates. A number of studies have conducted convergent validity investigations that compare the use of the internet with other survey implementation modes such as mail, telephone and in-person. All, but one, of these comparison studies is confounded different sample frames for the different modes of survey implementation. In this study we investigate differences in internet and mail survey modes holding the sample frame constant. This is done in the context of a choice-modelling study of improvements in the River Murray in Australia. We also investigate sample frame holding the survey mode (mail) constant. We find that survey mode (internet vs. mail) influences welfare estimates, and the internet welfare estimates are about 78 % of the mail welfare estimates on average. There is not a significant effect of sample frame (internet panel vs. postal addresses) on welfare estimates for implementation of a mail survey.
Boyle, K. J., Morrison, M., Hatton MacDonald, D., Duncan, R., & Rose, J. (2016). Investigating internet and mail implementation of stated-preference surveys while controlling for differences in sample frames. Environmental and Resource Economics, 64(3), 401-419. https://doi.org/10.1007/s10640-015-9876-2