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In an uncertain world, the actual result of changing behavior
may not always make
people better off. However, as a matter of rationality, people
are assumed to engage
only in behavior that they think ahead of time will make them better off. That is,
individuals will only pursue an activity if expected marginal benefits are greater than
expected marginal costs, or
E(MB) >
E(MC).
The rule of rational choice is simply
the rule of being sensible, and most economists
believe that individuals act
as if they are sensible and apply the rule of rational choice
to their daily lives
We can use marginal thinking to evaluate pollution levels.
We have to weigh the
expected marginal benefits of a cleaner environment against the expected marginal
costs of a cleaner environment. Zero pollution levels would be far too costly in terms
of what we would have to give up.
Just as we can have optimal (or best) levels of pollution that are greater than zero, the
same marginal thinking can be used to analyze crime and safety issues. What would it
cost society to have zero crime? It would probably be impossible to eliminate crime.
Regarding safety, the issue is not safe or unsafe products, but rather how much safety
consumers want. (For example, Peltzmans study of
car safety regulations and
increased reckless driving.)
In the News: Weighing the Benefits and Costs of Punting on Fourth Down