英文文献：Web surveys, sample bias and the travel cost method
英文文献作者：Fleming, Christopher M.,Cook, Averil
英文文献摘要：
Environmental economists have long used surveys to gather information about people's preferences. This is particularly true in the field of non-market valuation, where techniques such as contingent valuation, choice modelling and the travel cost method invariably employ some form of survey instrument. A recent innovation in survey methodology has been the advent of web-based surveys. While popular in many other disciplines, to date, very few non-market valuation studies have employed the Internet as a survey tool. A primary concern of non-market valuation practitioners is the potential sampling biases associated with web-based surveys and the effect this may have on valuation estimates. In this paper the results of two travel cost surveys, one conducted via conventional mail, the other via the Internet, are compared.