Sensitivity to scope has been studied in several research paradigms see section
3-6.. We are concerned here with a particular variant, the quantity design, in which
participants indicate their willingness to pay for a specified amount of a relatively
homogeneous good.3 The amount of the good is varied across groups of respondents.
A well known example of this experimental design is due to Desvousges et
al. 1992.. The question these authors put to their respondents can be paraphrased
as follows: ‘‘2,000, or 20,000, or 200,000. migrating birds die each year by drowning
in uncovered oil ponds, which the birds mistake for bodies of water. These deaths
could be prevented by covering the oil ponds with nets. How much money would
you be willing to pay to provide the needed nets?’’