Menus Subscribe Search

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

July 24 • 5:00 AM

In Praise of Our Short Attention Spans

Maybe there’s a good reason why it seems like there’s been a decline in our our ability to concentrate for a prolonged period of time.


July 24 • 4:00 AM

How Stereotypes Take Shape

New research from Scotland finds they’re an unfortunate product of the way we process and share information.


July 23 • 4:00 PM

Who Doesn’t Like Atheists?

The Pew Research Center asked Americans of varying religious affiliations how they felt about each other.


July 23 • 2:00 PM

We Need to Start Tracking Patient Harm and Medical Mistakes Now

Top patient-safety experts call on Congress to step in and, among other steps, give the Centers for Disease Control and Prevention wider responsibility for measuring medical mistakes.


July 23 • 12:19 PM

How a CEO’s Fiery Battle Speeches Can Shape Ethical Behavior

CEO war speech might inspire ethical decisions internally and unethical ones among competing companies.


July 23 • 12:00 PM

Why Do We Love the ‘Kim Kardashian: Hollywood’ Game?

It’s easy enough to turn yourself into a virtual celebrity, complete with fame and mansions—but it will likely cost you.


July 23 • 11:49 AM

Modern Technology Still Doesn’t Protect Americans From Deadly Landslides

No landslide monitoring or warning systems are being used to protect vulnerable communities.


July 23 • 10:00 AM

Outing the Death-Drug Distributors

Calling all hackers: It’s time to go Assange on capital punishment.


July 23 • 8:00 AM

The Surprising Appeal of Products That Require Effort to Use

New research finds they enable consumers to re-establish a feeling that they’re in control of their lives.



July 23 • 6:00 AM

How the Other Half Lifts: What Your Workout Says About Your Social Class

Why can’t triathletes and weightlifters get along?


July 23 • 5:02 AM

Battle of the Public Intellectuals: Edward Glaeser vs. Richard Florida

On gentrification and housing costs.


July 23 • 4:00 AM

Our Fear of Immigrants

Why did a group of fourth graders rally in support of an undocumented classmate while the citizens of Murrieta, California, tried to stop immigrant children from entering their town?


July 22 • 4:00 PM

Can Meditation Really Slow Aging?

Is there real science in the spiritualism of meditation? Jo Marchant meets a Nobel Prize-winner who thinks so.



July 22 • 2:00 PM

The Alabama Judge Who Refuses to Let Desegregation Orders Go Ignored

A federal judge in Alabama says a local school board has failed to meet legal mandate to integrate.


July 22 • 12:00 PM

On the Destinations of Species

It’s almost always easier to cross international borders if you’re something other than human.


July 22 • 10:51 AM

The Link Between Carbs, Gut Microbes, and Colon Cancer

Reduced carb intake among mice protected them from colon cancer.


July 22 • 10:47 AM

Irrational Choice Theory: The LeBron James Migration From Miami to Cleveland

Return migrants to Cleveland have been coming home in large numbers for quite some time. It makes perfect sense.


July 22 • 9:32 AM

This Time, Scalia Was Right

President Obama’s recess appointments were wrong and, worse, dangerous.


July 22 • 8:00 AM

On Vegas Strip, Blackjack Rule Change Is Sleight of Hand

Casino operators are changing blackjack payouts to give the house an even greater advantage. Is this a sign that Vegas is on its way back from the recession, or that the Strip’s biggest players are trying to squeeze some more cash out of visitors before the well runs dry?


July 22 • 6:00 AM

Label Me Confused

How the words on a bag of food create more questions than answers.


July 22 • 5:07 AM

Doubly Victimized: The Shocking Prevalence of Violence Against Homeless Women

An especially vulnerable population is surveyed by researchers.


July 22 • 4:00 AM

New Evidence That Blacks Are Aging Faster Than Whites

A large study finds American blacks are, biologically, three years older than their white chronological counterparts.



Follow us


Subscribe Now

How a CEO’s Fiery Battle Speeches Can Shape Ethical Behavior

CEO war speech might inspire ethical decisions internally and unethical ones among competing companies.

Modern Technology Still Doesn’t Protect Americans From Deadly Landslides

No landslide monitoring or warning systems are being used to protect vulnerable communities.

The Link Between Carbs, Gut Microbes, and Colon Cancer

Reduced carb intake among mice protected them from colon cancer.

The New Weapon Against Disease-Spreading Insects Is Big Data

Computer models that pinpoint the likely locations of mosquitoes and tsetse flies are helping officials target vector control efforts.

People Are Clueless About Placebos

Doctors know that sometimes the best medicine is no medicine at all. But how do patients feel about getting duped into recovery?

The Big One

Today, the United States produces less than two percent of the clothing purchased by Americans. In 1990, it produced nearly 50 percent. July/August 2014

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