When big companies (like, say, British Petroleum) wreak great havoc (like, say, by spilling millions of gallons of oil into the Gulf of Mexico), it can be good policy to make them compensate their victims (like, say, with a $20 billion claim fund). It can also be bad policy.
A.C. Pigou taught us that we get better outcomes when decisionmakers bear the costs of their actions. Ronald Coase taught us that Pigou’s lesson cuts two ways. The shrimp boats that are sitting idle today are sitting idle partly because BP decided to drill in the gulf, but also partly because the shrimpers chose to operate in the vicinity of an oil rig. In this case, making BP feel the costs of its own decisions entails insulating the shrimpers from the costs of theirs.
In this particular case, I’m inclined to believe that it’s a good thing for BP to pony up. But contrary to what I’ve been reading around the web, there’s absolutely nothing in economic theory to dictate that conclusion; instead the conclusion depends on the particulars of the case. Is it cheaper to deal with the problem of spills by encouraging oil companies to be more responsible, or by encouraging others to stay out of their way? That’s an empirical question. Theory can’t answer it.
The various commentators who think they can justify holding BP liable by crying the word “externality”—and stopping there—exhibit a commendable grasp of environmental economics circa 1930. But this is 2010.