Thinking and Deciding

432 FAIRNESS AND JUSTICE
but not ex-post equity. After the coin is flipped, the situation is just as inequitable
as Option 1. Option 3 has both ex-ante and ex-post equity. People generally prefer
Option 3 to Option 2, and Option 2 to Option 1. That is, people are concerned with
equity before the resolution of uncertainty as well as after. 3
In a less fanciful example, Peter Ubel and his colleagues (1996b) told subjects
(people waiting for jury duty), “All else equal, kidney transplants are more likely to
succeed if they are transplanted into patients who ‘match’ the kidney donor. The
number of successful transplants one year after transplant is eight out of ten for patients
with a complete match and seven out of ten for patients with a partial match.”
The subjects were asked to allocate 100 available kidneys among two groups: 100
with a complete match (hence 80% success rate) and 100 with a partial match (70%).
Most subjects allocated 50 kidneys to each group. (In other versions, the groups differed
by race or by socioeconomic status, but the results were essentially the same.)
When asked how to maximize the success rate, fewer than 20% of the subjects gave
the correct answer (all 100 to the 80%-success group), and most of these subjects
still allocated the kidneys equally.
In a similar example, Ubel et al. (1996a) found that many people would give a
screening test to everyone in a group of patients covered by the same health maintenance
organization (HMO) if the test would prevent 1,000 cancer cases rather than
give a test to half of the patients (picked at random) that would prevent 1,200 cancer
cases. Whether the test prevents cancer is the ex-post issue, and people were willing
to tolerate less prevention for the sake of more ex-ante equity.
Ubel, Baron, and Asch (2001) found that this bias was reduced when the group
was expanded. If subjects are told that the HMO actually covers two states and that
the test cannot be given in one of the states, some subjects switched their preference
to the test that prevented more cancers. It was as though they reasoned that, because
the “group” was now larger, they could not give the test to “everyone” anyway. So
they might as well aim for better consequences, given that “fairness” could not be
achieved. This result illustrates a potential problem with some nonutilitarian concepts
of distributive justice — namely, that the distributions they entail can change
as the group definition is changed. If groups are arbitrary, then the idea of fair distribution
is also arbitrary.
Typically, ex-post equity can be justified by the principle of declining marginal
utility. If we can redistribute the outcomes to make them more equal by taking from
one person and giving to another, we generally improve the situation (except for
incentive effects). In these cases, however, that reasoning does not apply, because
only two outcomes are possible. Ex-ante equity has no simple utilitarian justification.
3A similar example (from Petit, 1991) violates the sure-thing principle (Chapter 10). Consider the
following options:
1. Heads Mary wins; tails John wins.
2. Heads John wins; tails John wins.
3. Heads Mary wins; tails Mary wins.
4. Heads John wins; tails Mary wins.
Most people would prefer Option 1 to Option 2, because it is fair ex-ante. And they would prefer Option
4 to Option 3 for the same reason. But the outcome of “tails” is constant in both choices.