24 Oct 2009

The Problem With Pigou

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From an email I wrote to a group of colleagues who were arguing over whether it was really true that fossil fuel use only had negative externalities. (One of the guys was arguing that cheap energy confers benefits on society, just as surely as an opera house.)

Sorry I’m late replying to this; swamped with work. Consumer surplus
refers to the benefit consumers get from the availability of certain
markets, because presumably you keep buying units until the marginal
benefit of the next unit is lower than the unit price. So the idea is
that you gain a surplus on each of the inframarginal units. A lot of
people don’t see how a voluntary trade makes both people better off.
If a gallon of gas has a price of $2.50, then the consumer buys it and
at best is “even” because he swapped out $2.50 in cash for something
that is “worth” $2.50. But obviously that is wrong.

A positive externality means your actions shower benefits on other
people who aren’t in the actual market transaction. Textbook examples
are things like schooling and vaccination. An individual presumably
decides to learn to read, and get vaccinated (or at least his parents
force him to do these things) because the personal benefits outweigh
the personal costs. But it’s in my interest if other people become
literate and vaccinate themselves. (Let’s stipulate that we’re talking
about an effective vaccine. I know a lot of people don’t like the H1N1

The problem with externalities is that if you push it, just about
every action you take has a million positive and a million negative
externalities. E.g. if I put on smelly socks before going to work,
that’s a negative externality and the government ought to fine me, in
principle. Oh but maybe the odor causes others to think about
workplace odor, causing 5 people to use anti-perspirant who otherwise
wouldn’t have. Thus my wearing of smelly socks confers a positive
externality, and the government should subsidize me, in principle.

So [Mr. Colleague] is definitely right that there are positive externalities
from fossil fuel use, if only because I can dream up positive
externalities from any activity X.

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