Superstorm Sandy reminds us why it’s easy to underestimate danger

On Tuesday, as millions of people from Delaware to Connecticut awoke to homes and businesses damaged or destroyed, with no electricity and no certainty about when they’d have it back, millions of others in Boston and Washington awoke to a wet, breezy morning and a seemingly unnecessary day off.

With no more than a lot of leaves and branches on the ground and an occasional fallen tree, schools, businesses and public transportation remained closed in many areas that had braced for Superstorm Sandy but fortunately escaped the worst of its power. And while New York, which suffered so badly, looked smart for having taken such precautions, many people thought Washington, Boston and Philadelphia had overreacted.

From a public safety standpoint, every city that prepared was right to do so. But this contrast in public opinion highlights the subjective nature of individual risk perception.

Like Goldilocks with her porridge, sometimes our perceptions of risk are too hot — we worry more than the evidence warrants. Sometimes our perceptions are too cold — we don’t worry as much as the evidence warns. And sometimes our fears are just right. But given how important it is to our health and safety to assess risk just right, why do we so often get it wrong?

With natural disasters, many people don’t worry enough. General preparation for such events is poor, and only urgent alarms of an impending Frankenstorm send people shopping for batteries and bottled water. This time, while some prepared and others evacuated high-risk areas in New York and New Jersey, many didn’t take Sandy’s risks seriously or were “just plain stupid,” as New Jersey Gov. Chris Christie put it, and stayed in harm’s way.

Hospitals in New York lost power because electrical systems in their basements weren’t protected, and untested backup generators failed, too. Car owners left their vehicles on the streets and in the underground parking garages of Lower Manhattan and low-lying areas of Brooklyn and — surprise! — later found them submerged.

Why don’t people take natural disasters seriously enough? Some tell themselves that “it won’t happen to me” or “I’ve been through these storms before.” Psychologists call this optimism bias.

“I’m ready,” some say, reflecting a misplaced confidence that their flashlights, sandbags and backup generators will protect them from the ferocity of Mother Nature. The more control over a risk you think you have, the less worrisome it feels, no matter how false that sense of control might be.

We also tend to worry less about risky behaviors that afford us some benefit — such as living on the coast, where the beauty of the view causes some to play down the danger of ocean storms. Those who stay put to “protect my property” are also weighing risk vs. benefit, as are people who go down to the shore to watch the waves because “I may never see this again in my life!” And that may turn out to be true because of the dangerous thrill-seeking they’re doing.

Finally there is the problem of innumeracy — illiteracy about numbers. We’re lousy at probabilities. It’s a good bet (though I can give no odds) that most people who experienced this “once in a century” storm figure that such freakish weather is not likely to happen again soon. Sorry, but next year’s weather hasn’t gotten that memo. There are probabilistic patterns for assessing the risk of natural disasters over the long term. But the long term is much longer than our very brief lifetimes.