High discount rates tend to work against environmental responsibility. For
example, reinstatement costs at the end of a 20-year project discounted at 12%
are worth only a tenth of what they would have been at the start of the project.
A 40-year project reduces their value to a hundredth. But social cost–benefit
analysts have a responsibility to build environmental costs into assessments,
even if these costs may never be paid – the social cost–benefit analyst’s task is
to assess the full social benefits and costs of an activity, not to compromise with
de facto implementation.