The Trade-Off of Security

Security is a trade-off. This is something I have written about extensively, and is a notion critical to understanding the psychology of security. There’s no such thing as absolute security, and any gain in security always involves some sort of trade-off.

Security costs money, but it also costs in time, convenience, capabilities, liberties, and so on. Whether it’s trading some additional home security against the inconvenience of having to carry a key around in your pocket and stick it into a door every time you want to get into your house, or trading additional security from a particular kind of airplane terrorism against the time and expense of searching every passenger, all security is a trade-off.

I remember in the weeks after 9/11, a reporter asked me: “How can we prevent this from ever happening again?” “That’s easy,” I said, “simply ground all the aircraft.”

It’s such a far-fetched trade-off that we as a society will never make it. But in the hours after those terrorist attacks, it’s exactly what we did. When we didn’t know the magnitude of the attacks or the extent of the plot, grounding every airplane was a perfectly reasonable trade-off to make. And even now, years later, I don’t hear anyone second-guessing that decision.

It makes no sense to just look at security in terms of effectiveness. “Is this effective against the threat?” is the wrong question to ask. You need to ask: “Is it a good trade-off?” Bulletproof vests work well, and are very effective at stopping bullets. But for most of us, living in lawful and relatively safe industrialized countries, wearing one is not a good trade-off. The additional security isn’t worth it: isn’t worth the cost, discomfort, or unfashionableness. Move to another part of the world, and you might make a different trade-off.

We make security trade-offs, large and small, every day. We make them when we decide to lock our doors in the morning, when we choose our driving route, and when we decide whether we’re going to pay for something via check, credit card, or cash. They’re often not the only factor in a decision, but they’re a contributing factor. And most of the time, we don’t even realize it. We make security trade-offs intuitively.

These intuitive choices are central to life on this planet. Every living thing makes security trade-offs, mostly as a species–evolving this way instead of that way–but also as individuals. Imagine a rabbit sitting in a field, eating clover. Suddenly, he spies a fox. He’s going to make a security trade-off: should I stay or should I flee? The rabbits that are good at making these trade-offs are going to live to reproduce, while the rabbits that are bad at it are either going to get eaten or starve. This means that, as a successful species on the planet, humans should be really good at making security trade-offs.

And yet, at the same time we seem hopelessly bad at it. We get it wrong all the time. We exaggerate some risks while minimizing others. We exaggerate some costs while minimizing others. Even simple trade-offs we get wrong, wrong, wrong–again and again. A Vulcan studying human security behavior would call us completely illogical.

The truth is that we’re not bad at making security trade-offs. We are very well adapted to dealing with the security environment endemic to hominids living in small family groups on the highland plains of East Africa. It’s just that the environment of New York in 2007 is different from Kenya circa 100,000 BC. And so our feeling of security diverges from the reality of security, and we get things wrong.

There are several specific aspects of the security trade-off that can go wrong. For example:
The severity of the risk.
The probability of the risk.
The magnitude of the costs.
How effective the countermeasure is at mitigating the risk.
How well disparate risks and costs can be compared.

The more your perception diverges from reality in any of these five aspects, the more your perceived trade-off won’t match the actual trade-off. If you think that the risk is greater than it really is, you’re going to overspend on mitigating that risk. If you think the risk is real but only affects other people–for whatever reason–you’re going to underspend. If you overestimate the costs of a countermeasure, you’re less likely to apply it when you should, and if you overestimate how effective a countermeasure is, you’re more likely to apply it when you shouldn’t. If you incorrectly evaluate the trade-off, you won’t accurately balance the costs and benefits.

A lot of this can be chalked up to simple ignorance. If you think the murder rate in your town is one-tenth of what it really is, for example, then you’re going to make bad security trade-offs. But I’m more interested in divergences between perception and reality that can’t be explained that easily. Why is it that, even if someone knows that automobiles kill 40,000 people each year in the U.S. alone, and airplanes kill only hundreds worldwide, he is more afraid of airplanes than automobiles? Why is it that, when food poisoning kills 5,000 people every year and 9/11 terrorists killed 2,973 people in one non-repeated incident, we are spending tens of billions of dollars per year (not even counting the wars in Iraq and Afghanistan) on terrorism defense while the entire budget for the Food and Drug Administration in 2007 is only $1.9 billion?

It’s my contention that these irrational trade-offs can be explained by psychology. That something inherent in how our brains work makes us more likely to be afraid of flying than of driving, and more likely to want to spend money, time, and other resources mitigating the risks of terrorism than those of food poisoning. And moreover, that these seeming irrationalities have a good evolutionary reason for existing: they’ve served our species well in the past. Understanding what they are, why they exist, and why they’re failing us now is critical to understanding how we make security decisions. It’s critical to understanding why, as a successful species on the planet, we make so many bad security trade-offs.