In this paper, Chinese consumers' preferences and their willingness to pay (WTP) for non-genetically modified (GM) vegetable oil were elicited by a payment card approach. In addition to the conventional model, spike models, which were originally developed to evaluate public goods, were adopted in this paper. These spike models recognize the possibility of zero WTP and provide opportunities to analyze two correlated decision stages: whether to pay a premium for non-GM oil and how much the premium is. Results show that consumers behaved consistently in the two decision stages and there is a premium associated with non-GM oil.
