Saturday, August 04, 2007

Calculating our losses

King Banaian shakes his head wearily. Sometimes, bad things happen regardless of what we do:

As the blame game continues, I got to thinking about time to build. Roughly how long would it take to have rebuilt the bridge that fell, assuming that Governor Pawlenty had somehow been able to gaze into a crystal ball and foreseen the black swan?

I use black swan in the Taleb-ian sense. Unlike Matt's otherwise very sensible post [MNPublius], I don't think trying to figure out why the bridge fell is going to somehow improve policy. I make this point repeatedly to students -- you can sometimes do everything right and get a bad outcome due to randomness. Black swans are simply outliers -- they are things that just happen that cannot be expected within the realm of our experience. I think that until investigation concludes, you should reserve the possibility that the bridge collapse is a black swan event. (Or perhaps a gray swan, for those who've read Taleb.)

Apparently, Banaian has never built a house of cards! Banaian goes on to lecture us about marginal analysis as a method for allocating resources and making decisions:

Begin with the observation that no bridge can ever be perfectly safe. Rational allocation of scarce resources must involve marginal analysis: We allocate the money to make transportation safe up to the point where the marginal benefit of investing the dollar in project A is equal to that of project B is equal to that of project C, etc. And we invest only an amount where the increase of safety is worth the expense of providing it. I don't wait for the car 300 feet away that I judge to be traveling about 30 mph to pass before crossing the road; experience teaches that I can cross that road without incident. 99.999% of the time, it will be the case; every time I have done so before I have arrived to the other side safely. That doesn't mean the car will never hit me, just that the chance that it will is vanishingly small so that I do not allow it to disturb the decision that I'd rather be on the other side of the street now.

Banaian is right about one thing: finding the physical cause of the bridge collapse won't tell us much about public policy. That policy is made far upstream from the point where a bridge goes into the water. What the professor has given us is the unctuous, rational technocratic explanation of the bridge problem. If you accept his framing of the question, his solution seems inevitable. Shake your head in sorrow, tell the victims that your "heart goes out to them," and move on. The dollars have delivered their verdict.

Spot wants to talk about some of the elements of Banaian's framing.

Begin with the observation that no bridge can ever be made perfectly safe.

Who can argue with that? In the abstract, which is where the technocrat wants to argue, the statement is true. From this statement, Banaian wants you to conclude, boys and girls, that it is inevitable that every once in a while, the most heavily-traveled bridge in a state somewhere will just yield up its spirit and fall into the river. But that doesn't conform to what we know about bridges in general, and the 35W bridge in particular.

We know that bridges are subject to corrosion, wear and tear, and metal fatigue. From reports in media, some of which Spot and others have referred to, we also know that the 35W bridge had experienced metal fatigue and that the state—and the feds—were aware of it. Apparently, some MnDOT staffers were pretty exercised about the state of the bridge.

What we really know is that a bridge, being a mechanical device, will inevitably fail unless it is repaired or replaced. The risk of failure increases as the bridge ages. These things are just as true "no bridge can ever be made perfectly safe." Since we know bridges will fail unless cared for, and since we also know that the consequences of a failure will be, to use the governor's own term, "catastrophic," it seems sensible to be rigorous in inspection of and fixing of bridges. As Spot wrote before, God didn't knock the damn thing down.

Moreover, we know from news reports that transportation maintenance and repairs have been pushed back, sometimes by years, because of budgetary problems. It's like putting off backing up the hard drive on your computer until it's too late. You know it is going to fail sometime, yet you delude yourself into thinking that it won't be for a while yet. Then you have the "Aw s**t moment." Governor Pepsodent and his first mate Carol Molnau had their "Aw s**t moment" last Wednesday. The prudent computer operator has backups; the foolish one does not.

As the stewards of the public safety—that is what they are, after all—Pepsodent and Molnau should have focused on getting the bridge fixed—which certainly could have been done somehow—reducing the loads on it, or even closing it. But you see, boys and girls, bridge restrictions would have produced massive political pressure to raise the money to fix the bridge. And that would have been incompatible with Pepsodent and Molnau's governing philosophy and Pepsodent's desire to move out East. Now they're like the indolent computer operator caught without backups. A quarter-billion dollars or more behind the eight ball.

Roughly how long would it take to have rebuilt the bridge that fell, assuming that Governor Pawlenty had somehow been able to gaze into a crystal ball and foreseen the black swan?

We're about to find out, aren't we professor? We must always see the black swan in hard drives and bridges. The decision to play the percentages looks good until that moment it finally doesn't and one is reminded of that moment's inevitability. Banaian also errs in assuming that replacement of the bridge was the only option, intending of course to push the marginal analysis further into the realm of doing nothing.

It is of passing interest to Spot to know the physical cause of the bridge collapse: where the fatal fatigue occurred, what better anti-corrosion coatings could have been used, how the bridge may have been better designed and built. But Spot knows the proximate cause, that near cause that we can point to as the reason all those people plunged into the river: political decision making. It is a little like the man who suffers a fatal heart attack after eating bacon for every meal for twenty years. The death certificate may say myocardial infarction, but it was really the bacon.

There are some who counsel a refraining from assigning blame for the bridge collapse now. We can retrieve the whole bridge from the river, reassemble is somewhere, and conduct a careful accident analysis, but that won't do nearly as much good as identifying the public policy that is really the cause. And you really can't describe that policy without identifying its perpetrators.

Finally, Spot has a few words for you boys and girls to help you evaluate things said and written by technocrats like the professor in the future:

The social sciences, new creations of the mathematical obsession, are of course the principle example of the humanities deformed. The reduction of politics, economics, social problems and the arts to mathematical visions and obscure, hermetically sealed vocabularies may well be looked upon by those who come after us as one of the greatest follies of our civilization.

John Ralson Saul

When that case is made, boys and girls, you can be sure that Professor Banaian will be identified in the exhibits.

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