Chicago Working Paper in Law and Economics 2
sum of welfare equivalents (WEs) rather than the sum of CVs, where P’s WE is the amount of
money such that – paid to or from him in the project world – he is just as well off as in the status
quo, on the correct theory of well-being. Thus defined, CBA is agnostic across theories of well-
being, and in particular is not committed to the view that welfare and actual-preference-satisfaction
are equivalent. Because of this, when we discuss WEs, we will often not have a fixed number or
formula in mind; the concept of WE (unlike the concepts of CV and equivalent variation, for
example) is used as a placeholder to describe what dollar amount would be necessary under a given
theory, or cluster of theories, of well-being. Nonetheless, even without making strong
assumptions about the right theory of well-being, we will be able to derive some restrictions on
how WEs are determined.
The concept of WE is necessary because the actual preference theory of CBA must be
abandoned. Actual preferences are not necessarily constitutive of welfare because they can be
distorted, in various ways. For example, P may prefer the project to the status quo because he is
uninformed; with fuller information, he would prefer the status quo. Or, P’s preference for the
project may not track relevant criteria of objective value. The project harms innocent children; P,
who is a sadist, prefers the project just because it does that, and he retains this despicable
preference under full information. In these kinds of cases, traditional CBA equates the welfare
impact of the project upon P to his CV, which is a positive number. Yet most people would agree
that the ignorant or sadistic P, who prefers the project only in virtue of his ignorance or his sadism,
should not be counted as a project beneficiary, who helps tip the cost-benefit scale in the project’s
favor. But how should the project’s welfare impact upon P be calculated? At first glance, the
correct agency response to the problem of distorted preferences seems to be to ask what P would
hypothetically be willing to pay or accept if his preferences were relevantly undistorted (well-
informed, non-sadistic), and use that number rather than P’s CV in the cost-benefit calculus. The
problem here is that P continues to have his actual preferences, not his hypothetical preferences,
and his actual preferences – on the right theory of well-being – may have a significant effect on his
welfare. If P remains ignorant, and continues to prefer the project to the status quo, then the fact
that he would (under full information) have a valuation of, say, -$100 for the project hardly means
that the actual welfare effect of the project is -$100. And similarly for the sadistic P.
So agencies face a dilemma. On the one hand, CVs defined in terms of actual preferences
deviate from welfare, when such preferences are distorted. On the other hand, hypothetical
valuations in light of undistorted preferences may not capture the real welfare impact of projects
either. This Article takes a stab at solving that dilemma. The glib answer is that agencies should
aggregate WEs, not CVs or hypothetical CVs. But this glib answer is really just a promissory
note, because it remains to be seen how actual and undistorted preferences interact, for various
kinds of distortions, to produce WEs. A further problem, which also needs to be confronted, is
that the sum-of-WEs can deviate substantially from overall well-being because the marginal utility
of dollars depends upon the wealth of the person affected. (This is a well-known problem for
conventional CBA based on CVs; the use of WEs does not by itself solve this problem.) The glib
response here is that WEs should be weighted by a factor inversely proportional to wealth. As we
discuss in more detail below, that response overlooks the point that rich and poor people behave in
accordance with their actual wealth, not their hypothetical wealth.
Part I of the Article lays out, in compressed form, our view of CBA as a welfarist decision-
procedure, and further clarifies the idea of a WE.
3
Part II surveys agency practice and
3
Part I is based on Matthew D. Adler and Eric A. Posner, Rethinking Cost Benefit Analysis, 109
Yale L.J. 167 (1999), which contains further details and citations to the literature.