Low probability, high cost

Is L.A. prepared for the Big One? Doubtful. Not to minimize the efforts at shoring up buildings, roadways and bridges, but if a powerful earthquake were to hit in a vulnerable location of Southern California, it would undoubtedly result in many deaths and injuries, and it would cause great damage. We could greatly minimize those losses, but at too high a price - and for an event that might not happen for 40 years. So we try to be prudent without over-reaching. Be ready, but don't break the bank. BP tried to do much the same thing, but they did it horribly. NYT columnist Dave Leonhardt, writing in this Sunday's magazine, looks at the dangers of underestimating risk. Some snippets:

For all the criticism BP executives may deserve, they are far from the only people to struggle with such low-probability, high-cost events. Nearly everyone does. "These are precisely the kinds of events that are hard for us as humans to get our hands around and react to rationally," Robert N. Stavins, an environmental economist at Harvard, says. We make two basic -- and opposite -- types of mistakes. When an event is difficult to imagine, we tend to underestimate its likelihood. This is the proverbial black swan. Most of the people running Deepwater Horizon probably never had a rig explode on them. So they assumed it would not happen, at least not to them.

Similarly, Ben Bernanke and Alan Greenspan liked to argue, not so long ago, that the national real estate market was not in a bubble because it had never been in one before. Wall Street traders took the same view and built mathematical models that did not allow for the possibility that house prices would decline. And many home buyers signed up for unaffordable mortgages, believing they could refinance or sell the house once its price rose. That's what house prices did, it seemed.

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In a little-noticed provision in a 1990 law passed after the Exxon Valdez spill, Congress capped a spiller's liability over and above cleanup costs at $75 million for a rig spill. Even if the economic damages -- to tourism, fishing and the like -- stretch into the billions, the responsible party is on the hook for only $75 million. (In this instance, BP has agreed to waive the cap for claims it deems legitimate.) Michael Greenstone, an M.I.T. economist who runs the Hamilton Project in Washington, says the law fundamentally distorts a company's decision making. Without the cap, executives would have to weigh the possible revenue from a well against the cost of drilling there and the risk of damage. With the cap, they can largely ignore the potential damage beyond cleanup costs. So they end up drilling wells even in places where the damage can be horrific, like close to a shoreline. To put it another way, human frailty helped BP's executives underestimate the chance of a low-probability, high-cost event. Federal law helped them underestimate the costs.

Photo: How was the government of Haiti supposed to prepare for a natural disaster that was so unlikely to happen?