When an event is difficult to imagine, we tend to underestimate its likelihood

In retrospect, the pattern seems clear. Years before the Deepwater Horizon rig blew, BP was developing a reputation as an oil company that took safety risks to save money. An explosion at a Texas refinery killed 15 workers in 2005, and federal regulators and a panel led by James A. Baker III, the former secretary of state, said that cost cutting was partly to blame. The next year, a corroded pipeline in Alaska poured oil into Prudhoe Bay. None other than Joe Barton, a Republican congressman from Texas and a global-warming skeptic, upbraided BP managers for their “seeming indifference to safety and environmental issues.”

Much of this indifference stemmed from an obsession with profits, come what may. But there also appears to have been another factor, one more universally human, at work. The people running BP did a dreadful job of estimating the true chances of events that seemed unlikely — and may even have been unlikely — but that would bring enormous costs.

Perhaps the easiest way to see this is to consider what BP executives must be thinking today. Surely, given the expense of the clean-up and the hit to BP’s reputation, the executives wish they could go back and spend the extra money to make Deepwater Horizon safer. That they did not suggests that they figured the rig would be fine as it was.

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.

When the stakes are high enough, it falls to government to help its citizens avoid these entirely human errors. The market, left to its own devices, often cannot do so. Yet in the case of Deepwater Horizon, government policy actually went the other way. It encouraged BP to underestimate the odds of a catastrophe.

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.

Courtesy: New York Times Magazine.