Monday, June 13, 2011

Are Internet surveys an alternative to face-to-face interviews in contingent valuation?
Abstract: Internet is an increasingly popular data collection mode for stated preference research in environmental economics. However, little is known about how this survey mode may influence data quality and welfare estimates. As part of a national contingent valuation (CV) survey estimating willingness to pay (WTP) for biodiversity protection plans, we assign two groups of respondents either to an Internet or face-to-face (in-home) interview mode. Our design aims to better isolate measurement effects from sample composition effects by drawing both samples from the same sample frame. We find little evidence of social desirability bias in the interview setting or satisficing (shortcutting the response process) in the Internet survey. The share of “don't knows”, zeros and protest responses to the WTP question with a payment card is very similar between modes and equality of mean WTP cannot be rejected. Results are fairly encouraging for the use of Internet in CV as stated preferences do not seem to be significantly different or biased compared to face-to-face interviews.

► Internet is increasingly used as the survey mode in Stated Preference research.
► First well-controlled Contingent Valuation survey comparing Internet and face-to-face.
► Not significantly different mean WTP from Internet than face-to-face.
► Internet Contingent Valuation survey performs equally well as face-to-face

The Open-ended WTP question asked was
”Now we ask you to consider how much the two alternative plans are worth for your household. Think carefully through how much the 2.8% plan is worth compared to the current situation, before you give your final answer to the next question. Try to consider what would be a realistic annual amount given the budget of your household.Your household must choose whether to spend the amount on the forest conservation plan, or on other things.” - ”What is the most your householdalmost certainly is willing to pay in an additional annual tax earmarked to a public fund for increased forest conservation from today’s level of 1.4% to 2.8% of the productive forest area? Choose the highest amount, if anything, your householdalmost certainly will pay”.
The mean for the interview sample is somewhat higher at NOK 1819 than the NOK 1566 for the Internet sample with 1 NOK = 0.16 US $

The article is based on an original working paper entitled: "Internet CV surveys - a cheap, fast way to get large samples of biased values?" First draft April 28 2008 available at Presented at the World Congress of Environmental and Resource Economists, Montreal, Canada, 2. July 2010 under the title: "Benefits of biodiversity protection: Comparing in-person and internet CV survey modes” available at

by Henrik Lindhjem 1 and Ståle Navrud 2
1. Norwegian Institute for Nature Research, Gaustadalleen 21, N-0349 Oslo, Norway
2. Department of Economics and Resource Management, Norwegian University of Life Sciences, P.O. Box 5003, N-1432 Ås, Norway
Ecological Economics via Elsevier Science Direct
Volume 70, Issue 9; 15 July 2011; Pages 1628-1637
Special Section - Governing the Commons: Learning from Field and Laboratory Experiments
Keywords: Internet; Contingent valuation; Interviews; Survey mode; Biodiversity

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