Wednesday, December 10, 2008

Power Laws and Social Problems

Million-Dollar Murray is a fascinating article by Malcolm Gladwell about how "power laws" (really, heavy tailed distributions) can have surprising policy implications for dealing with social problems.

The article focuses most strongly on homelessness. The core of how power laws clash with our assumptions is summarized as:
That is what is so perplexing about power-law homeless policy. From an economic perspective the approach makes perfect sense. But from a moral perspective it doesn't seem fair. Thousands of people in the Denver area no doubt live day to day, work two or three jobs, and are eminently deserving of a helping hand—and no one offers them the key to a new apartment. […] Social benefits are supposed to have some kind of moral justification. We give them to widows and disabled veterans and poor mothers with small children. Giving the homeless guy passed out on the sidewalk an apartment has a different rationale. It's simply about efficiency.

Another issue considered is police brutality. After the Rodney King beating in Los Angeles, a special commission headed by Warren Christopher investigated the LAPD:
But what was the commission's most memorable observation? It was the story of an officer with a known history of doing things like beating up handcuffed suspects who nonetheless received a performance review from his superior stating that he "usually conducts himself in a manner that inspires respect for the law and instills public confidence." This is what you say about an officer when you haven't actually read his file, and the implication of the Christopher Commission's report was that the L.A.P.D. might help solve its problem simply by getting its police captains to read the files of their officers. The L.A.P.D.'s problem was a matter not of policy but of compliance. The department needed to adhere to the rules it already had in place, and that's not what a public hungry for institutional transformation wants to hear. Solving problems that have power-law distributions doesn't just violate our moral intuitions; it violates our political intuitions as well.

The third issue explored is pollution by automobile exhaust. This seems quite prosaic in comparison to the first two, but may be the best illustration of the way that we can incorrectly address a problem if we have an erroneous view of the distribution of the problem. For cars, we have:
Most cars, especially new ones, are extraordinarily clean. A 2004 Subaru in good working order has an exhaust stream that's just .06 per cent carbon monoxide, which is negligible. But on almost any highway, for whatever reason—age, ill repair, deliberate tampering by the owner—a small number of cars can have carbon-monoxide levels in excess of ten per cent, which is almost two hundred times higher. In Denver, five per cent of the vehicles on the road produce fifty-five per cent of the automobile pollution.
Given this heavy tailed distribution, alternatives to the customary annual inspection become more relevant:
[Donald Stedman, a chemist and automobile-emissions specialist at the University of Denver] proposes mobile testing instead. Twenty years ago, he invented a device the size of a suitcase that uses infrared light to instantly measure and then analyze the emissions of cars as they drive by on the highway. […] He says that cities should put half a dozen or so of his devices in vans, park them on freeway off-ramps around the city, and have a police car poised to pull over anyone who fails the test. A half-dozen vans could test thirty thousand cars a day. For the same twenty-five million dollars that Denver's motorists now spend on on-site testing, Stedman estimates, the city could identify and fix twenty-five thousand truly dirty vehicles every year, and within a few years cut automobile emissions in the Denver metropolitan area by somewhere between thirty-five and forty per cent. The city could stop managing its smog problem and start ending it.
Not mentioned by Gladwell is that this mobile testing would also have a moral benefit: costs could be shifted to polluters, instead of spreading the cost to everyone.

In summary, a fascinating article that connects a current scientific issue with current societal issues. I'm sure it only scratches the surface. No doubt, many other issues depend crucially on the distribution of underlying factors.

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