To start, here’s a fable called “The Charcoal-Burner and the Fuller.”
A CHARCOAL-BURNER carried on his trade in his own house. One day he met a friend, a Fuller, and entreated him to come and live with him, saying that they should be far better neighbors and that their housekeeping expenses would be lessened. The Fuller replied, “The arrangement is impossible as far as I am concerned, for whatever I should whiten, you would immediately blacken again with your charcoal.”This is a story about negative externalities. Were the charcoal-burner and fuller to move in together, the charcoal-burner’s trade would impose unwanted costs on the fuller’s. How might this problem be addressed?
Like will draw like.
In a traditional Pigovian analysis of the situation, the coal-burning’s harmful side effects might be regarded as justifying a correction. Perhaps the government ought to impose a tax on burning charcoal; the optimal tax would be set equal to the marginal external cost in terms of blackened garments. That would induce the charcoal-burner to consider the full costs of his choices, and therefore to reduce his charcoal-burning to the efficient level.
But Aesop’s story presages a more sophisticated Coasean analysis. As Ronald Coase observed, externalities are reciprocal in nature. To permit the burning of coal would harm the fuller -- but to restrict the burning of coal would harm the coal-burner. The presence of both activities is necessary for the externality to exist. And this draws our attention to the possibility of averting the harm by means other than reducing coal-burning. According to the least-cost avoider principle, an externality should be reduced or prevented by the party who can do so at the lowest cost. In the case at hand, the fuller can avoid the externality by not moving in with the charcoal-burner in the first place.
In most modern externality analysis, the story begins with two parties or activities that are already in conflict. But Aesop properly chooses to start his story before the conflict comes to be. Moreover, Aesop (like Coase) reminds us that externality problems can, at least sometimes, be solved or avoided by the interested parties themselves.