Heatmap reports on a study looking at the “long tail” of excess deaths in the wake of major hurricanes, and found that major storms are hundreds of times deadlier than anyone expected:
Several years ago, two economists and public policy researchers — Rachel Young and Solomon Hsiang, now of Princeton and Stanford — began to study a seemingly simple question: How many Americans do hurricanes kill each year? According to the federal government, the average hurricane kills 24 people after making landfall. That seemed likely to be a modest underestimate. Economists know that natural disasters can have a long tail of suffering; Hsiang expected the real number to be a “single digit multiple” of that figure — perhaps 50 or 100 people per storm.
Yet when they ran the numbers and looked at mortality in places affected by storms, they were initially perplexed by the results, Hsiang told me earlier this week. The numbers they came up with didn’t even make sense at first.
“It was months of us trying to understand what we were looking at,” Hsiang said. “And then once we realized what we were seeing, it was years of us checking our work to find what we missed.”
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Their study, which was published on Wednesday in Nature, finds that the average hurricane kills 7,000 to 11,000 people after making landfall in the United States. These previously uncounted deaths happened not during a storm or in its immediate aftermath, but as a long, slow trickle of mortality that plagues a region long after the clouds have cleared and floods have abated.
In any one year, the number of storm-related deaths is not very high. And yet a wave of excess deaths is visible in population data for at least 15 years after a storm hits an area, they found.
“It lasts for so many years, and because there’s so many storms hitting so many states, once you add up, it becomes this enormous number,” Hsiang told me. When added together, hurricanes’ long-term death toll exceeds American combat deaths in all wars, combined. The number so dwarfs previous estimates that it suggests tropical cyclones alone are a major determinant of public health across the United States.
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Officially, Hurricane Maria killed 64 people when it struck Puerto Rico in 2017. But when researchers surveyed households across the island months after the storm, they found the death toll was closer to 4,600. (The territory’s government later revised the official figure to 2,975.) These deaths were caused not by the cyclone’s high winds or torrential floods, but rather by secondary effects of the storm’s destruction. Maria took out the island’s power grid and road networks, for instance, and preventing people with heart attacks and strokes from reaching the hospital in time.
That paper was written six months after Maria struck the island; this new hurricane paper considers a wider time horizon, finding that more than 80,000 Americans die each year as a result of a hurricane, whenever it occurred.
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The paper may also help resolve a riddle in American public health. On average, Americans die earlier in the eastern half of the continental United States than in the western half. This effect is worst in the Gulf Coast and Southeast but persists to some degree in the Mid-Atlantic and Northeast.
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You can read more of the hurricane research here, in Nature.