Comparing an Internet Panel Survey to Mail and Phone Surveys on Willingness to Pay for Environmental Quality: A National Mode Test

Recently, the U.S. Environmental Protection Agency sought to determine whether a recruited Internet panel of respondents can be used to produce reliable estimates of willingness to pay for goods or services for which no formal market exists. Here we report the results of a national mode test comparing results from an Internet panel survey on air quality in national parks with the same questionnaire administered by mail and by phone. Sampling frame was held nearly constant by using national Random Digit Dialing samples with reverse-lookup of addresses for all three surveys. Weighting and matching the respondents did not eliminate significant demographic, behavioral, and attitudinal differences across modes. Results indicate a willingness to pay estimate derived from a probability-based Internet-panel survey is likely to be as accurate as that obtained from a well-designed mail survey.