Testing hypothetical bias in a choice experiment: An application to the value of the carbon footprint of Mandarin oranges

This study investigates “hypothetical bias,” defined as the difference in the willingness to pay for a product attribute between hypothetical and non-hypothetical conditions in a choice experiment, for the carbon footprint of mandarin oranges in Japan. We conducted the following four treatments: a non-hypothetical lab economic experiment, a hypothetical lab survey, a hypothetical online survey, and a hypothetical online survey with cheap-talk. Each treatment asked participants to choose one of three oranges based on price and carbon emissions level. Next, participants were asked to answer questions on demographics and the following three kinds of environmental factors: environmental consciousness, purchasing behavior for goods with eco-labels, and daily environmental behavior. Using the random parameter logit model, the willingness to pay per 1g of carbon emission reduction were 0.53 JPY, 0.52 JPY, 0.54 JPY, and 0.58 JPY in the non-hypothetical lab economic experiment, hypothetical lab survey, hypothetical online survey and hypothetical online survey with cheap-talk, respectively. The complete combinatorial test of the willingness to pay for carbon emission reductions indicates no hypothetical bias between any treatment combinations. Our findings reveal that environmental attributes for food are less likely to show hypothetical bias than other goods. The results of the main effect with an interaction term show that environmental consciousness reduces the coefficients of carbon emissions in all treatments. Therefore, a psychological scale is useful for showing whether hypothetical bias emerges with treatment or participants' personal backgrounds.