Devlin's Angle

December 2010

The Innumeracy Behind Airline Security

If ever I wanted to find a good example to illustrate the importance in today's society of ensuring that citizens achieve a basic level of quantitative literacy, the recent activities at the nation's airports provided it. Rather than spend increasing amounts of money, to say nothing of trampling on key provisions of our nation's founding constitution (in this case the Fourth Amendment), chasing a patently unachievable target, by spending a fraction of the money on elementary mathematical education we might achieve a lot more.

I fly a lot, over 100,000 miles a year, giving me a George Clooney like (Up in the Air movie), privileged 1.5 Million Miles status on United Airlines, and access to those exclusive lounges. Since a month rarely passes by without my sitting in an aircraft seat, airline safety matters to me in a very real way. My job requires that I travel a lot, so I am very aware of the risks. People die in aircraft disasters, and one day it could be me. But how likely is it?

In terms of my life being brought to a sudden, firey end in an aircraft, the cause is far more likely to be mechanical failure on the airplane or human error in the cockpit or in the airline traffic control room than it is to be a terrorist act. The airline security measures put in place shortly after 9/11 reduced the risk of dying in a terrorist attack well below the non-terrorist risks we accept every time we step on an airplane. There is absolutely no rational reason for the current level of panic-driven insanity, which as far as I can tell, having made many international trips in the past year alone, is not found in any other country, including the world's number one potential terrorist target, Israel. The only reason I can think of for the panic in the United States is a fundamental failure to appreciate the risks.

We want our President to protect us - at least presidents keep telling us that. There are many ways a president could keep us safe. A smart move would be to allocate protective resources according to the numbers.

A nation that was truly concerned about preventing avoidable deaths would ban smoking tomorrow. It kills 440,000 people each year, according to the CDC, which works out at 50 per hour. Unlike full body scanners and intrusive "pat downs" (and yes, I've had one), banning smoking, while unpopular in some quarters and a threat to the livelihood of some (not a factor to take lightly), would not ride roughshod over a constitutional right.

Or how about the president getting serious about eliminating drunk driving, which kills 15,000 people in the U.S. every year, with roughly eight drunk driving fatalities involving teenagers every day.

And don't let me start about diet, exercise, and obesity. Over 80M people in the United States have one or more forms of cardiovascular disease and over 150,000 Americans under 65 are killed by it each year; 73M have high blood pressure; 17M have coronary heart disease; over 6M suffer a stroke; and 6M have heart failure.

I'm not preaching or talking morals here. In our society we are free to make our own lifestyle decisions. It's about the math. Spending $85M to buy 500 full body scanners at $170,000 each, and turning the simple act of boarding an airplane into a circus, to try to eliminate a risk that is orders of magnitude less than many other risks people accept in their daily lives is a total waste of public funds, and is possible only because large numbers of people apparently don't do - or don't understand - the math.

It makes absolute sense to organize our lives and our society to minimize risks. But not at the expense of life itself. Life is risky. The risk of dying in your home due to a fall are far greater than of dying in a terrorist attack on an airplane. What do you do, stay in bed all the time? Actually, that isn't a good idea. In addition to the life threatening health risks that result from not getting up and exercising, there is also a greater risk of dying by falling out of bed than from dying in an airline terrorist attack.

As a species, we find ourselves with a sophisticated brain capable of rational decision making. Since the seventeenth century we have known how to assign reliable, meaningful numbers to life's risks so we can organize our lives appropriately. When we worry about a danger - an airline terrorist attack - that is far, far less likely than dying by drowning in our own bathtub, something has gone drastically wrong with our ability to act rationally.

Yes, the terrorist threat required action. (On a personal level, much of my mathematical research since 9/11 has been directed into ensuring we remain ahead of and catch the terrorists, so I do take the threat seriously.) We took that action in the early years after 9/11, and it has been highly effective. Have we eliminated the risk? No, that is not possible. But we have reduced it well below many of life's other risks.

Sitting in a narrow metal tube 39,000 feet in the air is not a situation evolution prepared us for. As a consequence, at the back of my mind as I board my next flight will be all kinds of risks. But terrorism will be so far down the list as to be out of sight. The TSA does not give me much, if any, feeling of security. The math does. I'd stake my life on the statistics. In fact I do, several times every month.

To repeat my original point. Life in today's society requires not only a workable level of literacy, it demands a basic level of numeracy as well. Until that level is reached, we will continue to squander scarce resources chasing unachievable and unnecessary goals, while far more important and easily attainable measures to improve lives and maintain the nation's safety and security are ignored. Now I am preaching.

Devlin's Angle is updated at the beginning of each month. Find more columns here. Follow Keith Devlin on Twitter at @nprmathguy.
Mathematician Keith Devlin (email: is the Executive Director of the Human-Sciences and Technologies Advanced Research Institute (H-STAR) at Stanford University and The Math Guy on NPR's Weekend Edition. His most recent book for a general reader is The Unfinished Game: Pascal, Fermat, and the Seventeenth-Century Letter that Made the World Modern, published by Basic Books.