Menus Subscribe Search

Follow us


Hey TSA, Racial Profiling Doesn’t Work

• November 30, 2010 • 3:34 PM

Looking at the math behind profiling meant to nab terrorists, computer scientist William Press realized it may be less effective than purely random sampling.

Arguments over racial profiling at the airport security line typically turn around the assumption that such screening, at least to some extent, works. The idea may be unsavory, but it sounds logical: If we target people with a higher probability of being terrorists — whether they have Saudi passports, beards or headscarves — we’d have a better chance of catching real terrorists in the process.

The question becomes one of morals. Is this the right thing to do? Does the societal benefit (catching more terrorists) outweigh the cost (compromising our ethics)?

William Press, a professor of computer science and integrative biology at the University of Texas at Austin, now realizes we don’t have to weigh this dilemma at all. Racial profiling, he has concluded, simply doesn’t work. Never mind how you feel about it. The math doesn’t add up.

Plucking out of line most of the vaguely Middle Eastern-looking men at the airport for heightened screening is no more effective at catching terrorists than randomly sampling everyone. It may even be less effective.

Press stumbled across this counterintuitive concept — sometimes the best way to find something is not to weight it by probability — in the unrelated context of computational biology. The parallels to airport security struck him when a friend mentioned he was constantly being pulled out of line at the airport.

“He’s not on any do-not-fly list, and it occurred to me it was exactly this phenomenon,” Press said. “Either explicitly or implicitly, there was some kind of profiling going on, and the same innocent individual was being screened over and over again. That draws resources away from the screening that  would find the bad guy. I realized those were basically the same problems.”

Racial profiling, in other words, doesn’t work because it devotes heightened resources to innocent people — and then devotes those resources to them repeatedly even after they’ve been cleared as innocent the first time. The actual terrorists, meanwhile, may sneak through while Transportation Security Administration agents are focusing their limited attention on the wrong passengers.

[class name=”dont_print_this”]

Idea Lobby

THE IDEA LOBBY
Miller-McCune's Washington correspondent Emily Badger follows the ideas informing, explaining and influencing government, from the local think tank circuit to academic research that shapes D.C. policy from afar.

[/class] Press tested the theory in a series of probability equations (the ambitious can check his math here and here).

“I was flabbergasted,” he said.

Sampling based on profiling is mathematically no more effective than uniform random sampling. The optimal equation, rather, turns out to be something called “square-root sampling,” a compromise between the other two methods.

“Crudely,” Press writes of his findings in the journal Significance, if certain people are “nine times as likely to be the terrorist, we pull out only three times as many of them for special checks. Surprisingly, and bizarrely, this turns out to be the most efficient way of catching the terrorist.”

This model minimizes the overemphasis on people like Press’ friend, creating the best trade-off between over- and under-screening profiled passengers.

“It’s just a little piece of math,” Press said, “that somehow has escaped the textbooks because you don’t need it very often.”

Square-root sampling, though, still represents a kind of profiling, and, Press adds, not one that could be realistically implemented at airports today. Square-root sampling only works if the profile probabilities are accurate in the first place — if we are able to say with mathematical certainty that some types of people are “nine times as likely to be the terrorist” compared to others. TSA agents in a crowded holiday terminal making snap judgments about facial hair would be far from this standard.

“The nice thing about uniform sampling is there’s nothing to be inaccurate about, you don’t need any data, it never can be worse than you expect,” Press said. “As soon as you use profile probabilities, if the profile probabilities are just wrong, then the strong profiling just does worse than the random sampling.”

Press would like to see policymakers get behind this conclusion, even if they can’t follow along with his algorithms.

“They don’t have to look at the details of the math,” he said. “I think that, when you come down to it, there’s an alternative that avoids the political minefield and is consistent with democratic values and is relatively easy to do.”

Randomly sample everyone.

Subscribe to Miller-McCune

Emily Badger
Emily Badger is a freelance writer living in the Washington, D.C. area who has contributed to The New York Times, International Herald Tribune and The Christian Science Monitor. She previously covered college sports for the Orlando Sentinel and lived and reported in France.

More From Emily Badger

A weekly roundup of the best of Pacific Standard and PSmag.com, delivered straight to your inbox.

Recent Posts

December 20 • 10:28 AM

Flare-Ups

Are my emotions making me ill?


December 19 • 4:00 PM

How a Drug Policy Reform Organization Thinks of the Children

This valuable, newly updated resource for parents is based in the real world.


December 19 • 2:00 PM

Where Did the Ouija Board Come From?

It wasn’t just a toy.


December 19 • 12:00 PM

Social Scientists Can Do More to Eradicate Racial Oppression

Using our knowledge of social systems, all social scientists—black or white, race scholar or not—have an opportunity to challenge white privilege.


December 19 • 10:17 AM

How Scientists Contribute to Bad Science Reporting

By not taking university press officers and research press releases seriously, scientists are often complicit in the media falsehoods they so often deride.


December 19 • 10:00 AM

Pentecostalism in West Africa: A Boon or Barrier to Disease?

How has Ghana stayed Ebola-free despite being at high risk for infection? A look at their American-style Pentecostalism, a religion that threatens to do more harm than good.


December 19 • 8:00 AM

Don’t Text and Drive—Especially If You’re Old

A new study shows that texting while driving becomes even more dangerous with age.


December 19 • 6:12 AM

All That ‘Call of Duty’ With Your Friends Has Not Made You a More Violent Person

But all that solo Call of Duty has.


December 19 • 4:00 AM

Food for Thought: WIC Works

New research finds participation in the federal WIC program, which subsidizes healthy foods for young children, is linked with stronger cognitive development and higher test scores.


December 18 • 4:00 PM

How I Navigated Life as a Newly Sober Mom

Saying “no” to my kids was harder than saying “no” to alcohol. But for their sake and mine, I had to learn to put myself first sometimes.


December 18 • 2:00 PM

Women in Apocalyptic Fiction Shaving Their Armpits

Because our interest in realism apparently only goes so far.


December 18 • 12:00 PM

The Paradox of Choice, 10 Years Later

Paul Hiebert talks to psychologist Barry Schwartz about how modern trends—social media, FOMO, customer review sites—fit in with arguments he made a decade ago in his highly influential book, The Paradox of Choice: Why More Is Less.


December 18 • 10:00 AM

What It’s Like to Spend a Few Hours in the Church of Scientology

Wrestling with thetans, attempting to unlock a memory bank, and a personality test seemingly aimed at people with depression. This is Scientology’s “dissemination drill” for potential new members.


December 18 • 8:00 AM

Gendering #BlackLivesMatter: A Feminist Perspective

Black men are stereotyped as violent, while black women are rendered invisible. Here’s why the gendering of black lives matters.


December 18 • 7:06 AM

Apparently You Can Bring Your Religion to Work

New research says offices that encourage talk of religion actually make for happier workplaces.


December 18 • 6:00 AM

The Very Weak and Complicated Links Between Mental Illness and Gun Violence

Vanderbilt University’s Jonathan Metzl and Kenneth MacLeish address our anxieties and correct our assumptions.


December 18 • 4:00 AM

Should Movies Be Rated RD for Reckless Driving?

A new study finds a link between watching films featuring reckless driving and engaging in similar behavior years later.


December 17 • 4:00 PM

How to Run a Drug Dealing Network in Prison

People tend not to hear about the prison drug dealing operations that succeed. Substance.com asks a veteran of the game to explain his system.


December 17 • 2:00 PM

Gender Segregation of Toys Is on the Rise

Charting the use of “toys for boys” and “toys for girls” in American English.


December 17 • 12:41 PM

Why the College Football Playoff Is Terrible But Better Than Before

The sample size is still embarrassingly small, but at least there’s less room for the availability cascade.


December 17 • 11:06 AM

Canadian Kids Have a Serious Smoking Problem

Bootleg cigarette sales could be leading Canadian teens to more serious drugs, a recent study finds.


December 17 • 10:37 AM

A Public Lynching in Sproul Plaza

When photographs of lynching victims showed up on a hallowed site of democracy in action, a provocation was issued—but to whom, by whom, and why?


December 17 • 8:00 AM

What Was the Job?

This was the year the job broke, the year we accepted a re-interpretation of its fundamental bargain and bought in to the push to get us to all work for ourselves rather than each other.


December 17 • 6:00 AM

White Kids Will Be Kids

Even the “good” kids—bound for college, upwardly mobile—sometimes break the law. The difference? They don’t have much to fear. A professor of race and social movements reflects on her teenage years and faces some uncomfortable realities.



Follow us


Don’t Text and Drive—Especially If You’re Old

A new study shows that texting while driving becomes even more dangerous with age.

Apparently You Can Bring Your Religion to Work

New research says offices that encourage talk of religion actually make for happier workplaces.

Canadian Kids Have a Serious Smoking Problem

Bootleg cigarette sales could be leading Canadian teens to more serious drugs, a recent study finds.

The Hidden Psychology of the Home Ref

That old myth of home field bias isn’t a myth at all; it’s a statistical fact.

The Big One

One in two United States senators and two in five House members who left office between 1998 and 2004 became lobbyists. November/December 2014

Copyright © 2014 by Pacific Standard and The Miller-McCune Center for Research, Media, and Public Policy. All Rights Reserved.