In order to express their preferences for a given type of coffee, respondents
were asked about their willingness to pay of the eight coffee profiles, in
comparison with a price of e1.87 for the reference profile. Since the orthogonal
design was representative for all combinations of attribute levels, the
four profiles with a label only differed from the four profiles without a label
in terms of the label itself. Therefore, we could determine the willingness to
pay for a fair-trade label as the difference between the average price of the
coffee profiles with a label and the coffee profiles without a label (i.e., the
price premium of fair-trade coffee).