Mj. Kealy et Rw. Turner, A TEST OF THE EQUALITY OF CLOSED-ENDED AND OPEN-ENDED CONTINGENT VALUATIONS, American journal of agricultural economics, 75(2), 1993, pp. 321-331
A test is developed to find whether open-ended and closed-ended contin
gent valuation mechanisms lead to significantly different results. The
test is based on joint estimation of willingness to pay responses to
open- and closed-ended questions asked of the same sample of individua
ls. In a public good example, individuals do respond differently depen
ding on question format. Possible explanations include different incen
tives for strategic behavior and respondents' lack of familiarity with
the open-ended question type. No differences in willingness to pay we
re found in a private good example.