Doing the Math on Mexican Drug Wars

The New York Times
By Viridiana Rios

Cambridge, Massachusetts — I am at the toll. Mexico is in front of me: the neighborhoods where the walls go unpainted; the fence, the patrollers, the river. I want to cross it to eat pulparindos, horchata and frijoles; to call my mother using a payphone that takes my pesos and has a Spanish-speaking operator; to buy the local gossip magazine. Home is 10 meters away.

But I am scared to cross the border.

My friend and fellow investigator receives a text message. It’s from a member of the drug cartel we have arranged to meet. “Let’s meet on the Mexican side,” the message says. “If Harvard has decided to come to hell, the city will remain calm.” We sit silently, wondering. Should we cross?

I was born in Mexico City, in a world that seems less and less familiar to me. I live now in the opposite corner of the continent. I am training to be a political scientist at Harvard. My passion has remained the afflictions of my homeland, but at Harvard I have found new ways to address them, to use mathematical models — matrices, vectors, equations, regressions — to understand the Mexican drug crisis.

So here I was last summer with my friend Alfredo Corchado, a reporter for the Dallas Morning News, on a trip home to gather information firsthand on the war among the Mexican drug cartels.

The work feels urgent. The cartels have caused the largest spike in violence that Mexico has experienced in recent times. In the last three years, drug-related violence has killed some 17,000 people, according to The New York Times. More journalists have been killed than in any other Western hemisphere country.

A decaying blue Chevy pulls up to us at the border crossing. We are holding our passports, waiting to be waved through. The Chevy slows down and aligns itself precisely with our car. In the passenger seat is a middle-aged man. He stares right at me, moving his lips, even though he knows that I can hear nothing.

He points at me. He smiles. We have been warned; they know we’re here. They always keep an eye on Alfredo. They don’t like the question-asking kind of people, and we are here to ask questions. They cannot kill me in America, I think to myself. In 10 minutes, when I am home, they will be able to.

It may seem strange to examine this shadowy world with equations. But mathematics is transforming the social sciences. In the same way that physicists can predict the movement of atoms in space, we can use mathematics to model how individuals and groups will make decisions and interact in a society.

It used to be that social scientists relied on intuition to understand social problems. But human intuition can go wrong. It is difficult to keep track of every factor in the interaction of millions of human beings. Human logic can be deceived by personal points of view, and, as psychological research has shown, humans see false patterns even when randomness is the norm. Mathematics is cold-headed; it cannot go wrong.

So here I am, waiting at the border, on a mission to understand, with my equations, who is at risk of becoming a drug trafficker, how labor incentives affect crime rates and violence, why kidnapping and extortion and homicide have spiked in recent years.

In this violent world, with the man in the blue Chevy whispering at me behind the window, math is my shield. Speaking up about drugs is in these parts a dangerous game. But not if you speak in the language of sigma and conditional expectations. Math protects me from the immediacy of the violence, and it protects me from them.

The beauty of my method lies in its simplicity. With mathematics I’m able to codify and simplify reality to make it manageable and, more important, malleable. I represent each possible individual as an equation in which each term symbolizes tastes, goals, profession and abilities. All people get portrayed: Policemen, politicians, citizens and drug cartels start living in this mathematical world as planes and hyperplanes and, as in real life, they interact and affect one another, sometimes colluding, sometimes colliding, sometimes neither.

I then use optimization to predict the form of interaction that will be the most probable to emerge and remain over time. Math starts speaking. It tells me, for example, under what conditions the outcome would be a drug war; when would the government prefer to cooperate with cartels; or when cruel intra-cartel purges will become the norm.

Things become even more fascinating. For example, what would be the maximum percentage of the Mexican population that could turn to drug trafficking if wage inequality doubled. Simple:

In this abstract microcosmos, reality can be frozen or just slightly changed. I move and look at my hyperplanes from different angles. Let’s change the penalty code. No, let’s increase patrolling. Or reduce wages. Allow less contact between policemen and dealers. Assume the police force is corrupt. Assume it is not. I solve the equations and there it is. My answers come as Greek letters and probabilities.

I know, I know, this is weird.

I have always wanted to contribute to Mexico’s well-being. I once believed that the way to do so was to study economics and political science and then work for the government. But I never expected that my means of trying to save my country would be math.

Now I surprise myself from time to time in doing things that three years ago I did not even know were possible.

The other day, in Laredo, I saw a large group of Mexican women, all around my age, in great shape, waiting for the bus.

“Those are the maids,” my driver told me. “They walk from their Mexican homes to the border every day, then take the bus to their American employers, before taking the bus back to the border each night and walking home.”

My brain took off. This was interesting. This can be mathematically modeled, I whispered to myself.