A tale of two storms

Sep 24, JDN 2458021

There were two severe storm events this past week; one you probably heard a great deal about, the other, probably not. The first was Hurricane Irma, which hit the United States and did most of its damage in Florida; the second was Typhoon Doksuri, which hit Southeast Asia and did most of its damage in Vietnam.

You might expect that this post is going to give you more bad news. Well, I have a surprise for you: The news is actually mostly good.

The death tolls from both storms were astonishingly small. The hurricane is estimated to have killed at least 84 people, while the typhoon has killed at least 26. This result is nothing less than heroism. The valiant efforts of thousands of meteorologists and emergency responders around the world has saved thousands of lives, and did so both in the wealthy United States and in impoverished Vietnam.

When I started this post, I had expected to see that the emergency response in Vietnam would be much worse, and fatalities would be far higher; I am delighted to report that nothing of the sort was the case, and Vietnam, despite their per-capita GDP PPP of under $6,000, has made emergency response a sufficiently high priority that they saved their people just about as well as Florida did.

To get a sense of what might have happened without them, consider that 1.5 million homes in Florida were leveled by the hurricane, and over 100,000 homes were damaged by the typhoon. Vietnam is a country of 94 million people. Florida has a population of 20 million. (The reason Florida determines so many elections is that it is by far the most populous swing state.) Without weather forecasting and emergency response, these death figures would have been in the tens of thousands, not the dozens.

Indeed, if you know statistics and demographics well, these figures become even more astonishing: These death rates were almost indistinguishable from statistical noise.

Vietnam’s baseline death rate is about 5.9 per 1,000, meaning that they experience about 560,000 deaths in any given year. This means that over 1500 people die in Vietnam on a normal day.

Florida’s baseline death rate is about 6.6 per 1,000, actually a bit higher than Vietnam’s, because Florida’s population skews so much toward the elderly. Therefore Florida experiences about 130,000 deaths per year, or 360 deaths on a normal day.

In both Vietnam and Florida, this makes the daily death probability for any given person about 0.0017%. A random process with a fixed probability of 0.0017% over a population of n people will result in an average of 0.0017n events, but with some variation around that number. The standard deviation is actually sqrt(p(1-p)n) = 0.004 sqrt(n). When n = 20,000,000 (Florida), this results in a standard deviation of 18. When n = 94,000,000 (Vietnam), this results in a standard deviation of 40.

This means that the 26 additional deaths in Vietnam were within one standard deviation of average! They basically are indistinguishable from statistical noise. There have been over a hundred days in Vietnam where an extra 26 people happened to die, just in the past year. Weather forecasting took what could have been a historic disaster and turned it into just another bad day.

The 84 additional deaths in Florida are over four standard deviations away from average, so they are definitely distinguishable from statistical noise—but this still means that Florida’s total death rate for the year will only tick up by 0.6%.

It is common in such tragedies to point out in grave tones that “one death is too many”, but I maintain that this is not actually moral wisdom but empty platitude. No conceivable policy is ever going to reduce death rates to zero, and the people who died of heart attacks or brain aneurysms are every bit as dead as the people who died from hurricanes or terrorist attacks. Instead of focusing on the handful of people who died because they didn’t heed warnings or simply got extraordinarily unlucky, I think we should be focusing on the thousands of people who survived because our weather forecasters and emergency responders did their jobs so exceptionally well. Of course if we can reduce the numbers even further, we should; but from where I’m sitting, our emergency response system has a lot to be proud of.

Of course, the economic damage of the storms was substantially greater. The losses in destroyed housing and infrastructure in Florida are projected at over $80 billion. Vietnam is much poorer, so there simply isn’t as much infrastructure to destroy; total damage is unlikely to exceed $10 billion. Florida’s GDP is $926 billion, so they are losing 8.6%; while Vietnam’s GDP is $220 billion, so they are still losing 4.5%. And of course the damage isn’t evenly spread across everyone; those hardest hit will lose perhaps their entire net wealth, while others will feel absolutely nothing.

But economic damage is fleeting. Indeed, if we spend the government money we should be, and take the opportunity to rebuild this infrastructure better than it was before, the long-run economic impact could be positive. Even 8.6% of GDP is less than five years of normal economic growth—and there were years in the 1950s where we did it in a single year. The 4.6% that Vietnam lost, they should make back within a year of their current economic growth.

Thank goodness.

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