If we take the survey results at face value, then it would be reasonable to interpret the $8.5 million annual willingness to pay as the aggregate annual option price. If the costs of the unit were certain, then this would be the appropriate benefit measure. As discussed in Chapter 13, however, there are many reasons why we might be sceptical of the accuracy of such a willingness-to-pay estimate.

a. The aggregate of individuals’ annual option prices for the unit.

b. The annual total expected gain in social surplus from use of the unit.

c. The annual aggregate option value for the unit.