JDN 2457202 EDT 17:52.

The 1992 Bill Clinton campaign had a slogan, “It’s the economy, stupid.”: A snowclone I’ve used on occasion is “it’s the externalities, stupid.” (Though I’m actually not all that fond of calling people ‘stupid’; though occasionally true is it never polite and rarely useful.) Externalities are one of the most important concepts in economics, and yet one that even all too many economists frequently neglect.

Fortunately for this one, I really don’t need much math; the concept isn’t even that complicated, which makes it all the more mysterious how frequently it is ignored. An externality is simply an effect that an action has upon those who were not involved in choosing to perform that action.

All sorts of actions have externalities; indeed, much rarer are actions that don’t. An obvious example is that punching someone in the face has the externality of injuring that person. Pollution is an important externality of many forms of production, because the people harmed by pollution are typically not the same people who were responsible for creating it. Traffic jams are created because every car on the road causes a congestion externality on all the other cars.

All the aforementioned are negative externalities, but there are also positive externalities. When one individual becomes educated, they tend to improve the overall economic viability of the place in which they live. Building infrastructure benefits whole communities. New scientific discoveries enhance the well-being of all humanity.

Externalities are a fundamental problem for the functioning of markets. In the absence of externalities—if each person’s actions only affected that one person and nobody else—then rational self-interest would be optimal and anything else would make no sense. In arguing that rationality is equivalent to self-interest, generations of economists have been, tacitly or explicitly, assuming that there are no such things as externalities.

This is a necessary assumption to show that self-interest would lead to something I discussed in an earlier post: Pareto-efficiency, in which the only way to make one person better off is to make someone else worse off. As I already talked about in that other post, Pareto-efficiency is wildly overrated; a wide variety of Pareto-efficient systems would be intolerable to actually live in. But in the presence of externalities, markets can’t even guarantee Pareto-efficiency, because it’s possible to have everyone acting in their rational self-interest cause harm to everyone at once.

This is called a tragedy of the commons; the basic idea is really quite simple. Suppose that when I burn a gallon of gasoline, that makes me gain 5 milliQALY by driving my car, but then makes everyone lose 1 milliQALY in increased pollution. On net, I gain 4 milliQALY, so if I am rational and self-interested I would do that. But now suppose that there are 10 people all given the same choice. If we all make that same choice, each of us will gain 1 milliQALY—and then lose 10 milliQALY. We would all have been better off if none of us had done it, even though it made sense to each of us at the time. Burning a gallon of gasoline to drive my car is beneficial to me, more so than the release of carbon dioxide into the atmosphere is harmful; but as a result of millions of people burning gasoline, the carbon dioxide in the atmosphere is destabilizing our planet’s climate. We’d all be better off if we could find some way to burn less gasoline.

In order for rational self-interest to be optimal, externalities have to somehow be removed from the system. Otherwise, there are actions we can take that benefit ourselves but harm other people—and thus, we would all be better off if we acted to some degree altruistically. (When I say things like this, most non-economists think I am saying something trivial and obvious, while most economists insist that I am making an assertion that is radical if not outright absurd.)

But of course a world without externalities is a world of complete isolation; it’s a world where everyone lives on their own deserted island and there is no way of communicating or interacting with any other human being in the world. The only reasonable question about this world is whether we would die first or go completely insane first; clearly those are the two things that would happen. Human beings are fundamentally social animals—I would argue that we are in fact more social even than eusocial animals like ants and bees. (Ants and bees are only altruistic toward their own kin; humans are altruistic to groups of millions of people we’ve never even met.) Humans without social interaction are like flowers without sunlight.

Indeed, externalities are so common that if markets only worked in their absence, markets would make no sense at all. Fortunately this isn’t true; there are some ways that markets can be adjusted to deal with at least some kinds of externalities.

One of the most well-known is the Coase theorem; this is odd because it is by far the worst solution. The Coase theorem basically says that if you can assign and enforce well-defined property rights and there is absolutely no cost in making any transaction, markets will automatically work out all externalities. The basic idea is that if someone is about to perform an action that would harm you, you can instead pay them not to do it. Then, the harm to you will be prevented and they will incur an additional benefit.

In the above example, we could all agree to pay $30 (which let’s say is worth 1 milliQALY) to each person who doesn’t burn a gallon of gasoline that would pollute our air. Then, if I were thinking about burning some gasoline, I wouldn’t want to do it, because I’d lose the $300 in payments, which costs me 10 milliQALY, while the benefits of burning the gasoline are only 5 milliQALY. We all reason the same way, and the result is that nobody burns gasoline and actually the money exchanged all balances out so we end up where we were before. The result is that we are all better off.

The first thought you probably have is: How do I pay everyone who doesn’t hurt me? How do I even find all those people? How do I ensure that they follow through and actually don’t hurt me? These are the problems of transaction costs and contract enforcement that are usually presented as the problem with the Coase theorem, and they certainly are very serious problems. You end up needing some sort of government simply to enforce all those contracts, and even then there’s the question of how we can possibly locate everyone who has ever polluted our air or our water.

But in fact there’s an even more fundamental problem: This is extortion. We are almost always in the condition of being able to harm other people, and a system in which the reason people don’t hurt each other is because they’re constantly paying each other not to is a system in which the most intimidating psychopath is the wealthiest person in the world. That system is in fact Pareto-efficient (the psychopath does quite well for himself indeed); but it’s exactly the sort of Pareto-efficient system that isn’t worth pursuing.

Another response to externalities is simply to accept them, which isn’t as awful as it sounds. There are many kinds of externalities that really aren’t that bad, and anything we might do to prevent them is likely to make the cure worse than the disease. Think about the externality of people standing in front of you in line, or the externality of people buying the last cereal box off the shelf before you can get there. The externality of taking the job you applied for may hurt at the time, but in the long run that’s how we maintain a thriving and competitive labor market. In fact, even the externality of ‘gentrifying’ your neighborhood so you can no longer afford it is not nearly as bad as most people seem to think—indeed, the much larger problem seems to be the poor neighborhoods that don’t have rising incomes, remaining poor for generations. (It also makes no sense to call this “gentrifying”; the only landed gentry we have in America is the landowners who claim a ludicrous proportion of our wealth, not the middle-class people who buy cheap homes and move in. If you really want to talk about a gentry, you should be thinking Waltons and Kochs—or Bushs and Clintons.) These sorts of minor externalities that are better left alone are sometimes characterized as pecuniary externalities because they usually are linked to prices, but I think that really misses the point; it’s quite possible for an externality to be entirely price-related and do enormous damage (read: the entire financial system) and to have little or nothing to do with prices and still be not that bad (like standing in line as I mentioned above).

But obviously we can’t leave all externalities alone in this way. We can’t just let people rob and murder one another arbitrarily, or ignore the destruction of the world’s climate that threatens hundreds of millions of lives. We can’t stand back and let forests burn and rivers run dry when we could easily have saved them.

The much more reasonable and realistic response to externalities is what we call government—there are rules you have to follow in society and punishments you face if you don’t. We can avoid most of the transaction problems involved in figuring out who polluted our water by simply making strict rules about polluting water in general. We can prevent people from stealing each other’s things or murdering each other by police who will investigate and punish such crimes.

This is why regulation—and a government strong enough to enforce that regulation—is necessary for the functioning of a society. This dichotomy we have been sold about “regulations versus the market” is totally nonsensical; the market depends upon regulations. This doesn’t justify any particular regulation—and indeed, an awful lot of regulations are astonshingly bad. But some sort of regulatory system is necessary for a market to function at all, and the question has never been whether we will have regulations but which regulations we will have. People who argue that all regulations must go and the market would somehow work on its own are either deeply ignorant of economics or operating from an ulterior motive; some truly horrendous policies have been made by arguing that “less government is always better” when the truth is nothing of the sort.

In fact, there is one real-world method I can think of that actually comes reasonably close to eliminating all externalities—and it is called social democracy. By involving everyone—democracy—in a system that regulates the economy—socialism—we can, in a sense, involve everyone in every transaction, and thus make it impossible to have externalities. In practice it’s never that simple, of course; but the basic concept of involving our whole society in making the rules that our society will follow is sound—and in fact I can think of no reasonable alternative.

We have to institute some sort of regulatory system, but then we need to decide what the regulations will be and who will control them. If we want to instead vest power in a technocratic elite, how do you decide whom to include in that elite? How do we ensure that the technocrats are actually better for the general population if there is no way for that general population to have a say in their election? By involving as many people as we can in the decision-making process, we make it much less likely that one person’s selfish action will harm many others. Indeed, this is probably why democracy prevents famine and genocide—which are, after all, rather extreme examples of negative externalities.