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Hundreds of hidden graves have been reported in Mexico. Here, forensic technicians overlook the likely site of a hidden grave near Monterrey.

Daniel Becerril/Reuters Pictures

Mapping Mexico’s hidden graves

MEXICO CITY—More than 30,000 people have disappeared without a trace in Mexico, most since violence skyrocketed after the government began battling drug cartels in 2006. Police investigations rarely solve such crimes, so many families are left to search on their own for the hidden graves that may hold their relatives. Last week, a team of data scientists and human rights researchers released a new tool for the searchers: a map predicting which municipalities in Mexico are most likely to house hidden graves.

“Without a doubt these hidden graves are one of the most critical signs of the human rights crisis we’re experiencing in Mexico,” says Denise González, coordinator of the Human Rights program at the Ibero-American University (Ibero) here, and a participant in the project. The Mexican government has reported 200 or so—a considerable undercount, activists say. After 2 years of scouring local and national press reports, González’s team documented 390 hidden graves discovered from 2009 to 2014, containing at least 1418 bodies. “I’m convinced we have more information about clandestine graves than the government itself,” González says. Mexico’s Attorney General’s office did not respond to request for comment. When Patrick Ball was introduced to Ibero’s database, the director of research at the Human Rights Data Analysis Group in San Francisco, California, saw an opportunity to turn the data into a predictive model. Ball, who has used similar models to document human rights violations from Syria to Guatemala, soon invited Data Cívica, a Mexico City–based nonprofit that creates tools for analyzing data, to join the project.

The team built its model using data from municipalities where hidden graves were reported in the media from 2013 to 2016. They classified each according to 35 geographic and socioeconomic variables, including murder rate, average level of education, and distance to the U.S. border. Their model then found municipalities with similar characteristics and determined the likelihood that they, too, would contain hidden graves.

The team unveiled its findings at a press conference last Thursday. In addition to 43 municipalities with hidden graves publicly reported in 2016—mostly in the states of Veracruz and Guerrero—the model identified 45 other municipalities as having a 70% or higher chance of containing unreported graves. Topping that list is Coyuca de Benítez in Guerrero, with an 86% chance. Five of the 10 with the highest probabilities—including Nogales, Sonora, and Juarez, Chihuahua—are in states along the U.S. border. Places least likely to contain hidden graves include the southern states of Quintana Roo and Yucatán.

Where the bodies may be buried

Researchers predicted which municipalities in Mexico were most likely to contain hidden graves in 2016, using a new statistical model. Municipalities in Guerrero, Michoacán, and along the northern border were most likely to contain undiscovered hidden graves.

Credits: (Graphic) J. You/Science; (Data) Data Cívica/Universidad Iberoamericana

“It’s very innovative,” says Jan Jarab, representative for the United Nations High Commissioner for Human Rights here. “And it’s not just academic—it could be of very practical use in the searches.”

But Teresa Vera Alvarado, a Mexico City resident who joined search brigades after her sister disappeared, thinks that because the model is based on press reports, it probably still leaves out the majority of hidden graves. The Mexican press faces censorship and threats from both organized crime and the government; according to The New York Times, more than 100 Mexican journalists have been murdered since 2000, and 25 others have disappeared. The families of the disappeared—who are carrying out most of the searches—are the best source of information, she says. To take their knowledge into account, González and her team will begin to meet with searchers in September.

Mónica Meltis, the executive director of Data Cívica here, agrees that many graves may remain invisible to the model, because they could follow different patterns than those reported in the press. Nevertheless, each discovery feeds the model new information and makes it more powerful, she says. “We can use scientific tools to shed light on what we haven’t yet been able to observe.”

Jorge Ruíz, a human rights researcher at Ibero, hopes the model’s stark results will push the government to finally act. The state—not the families—should be searching for hidden graves, he says. “We want to obligate the government to assume more responsibility for disappearances in Mexico.” Meltis agrees: “If the government really wants to search, like it says it does—well, search! Here’s a guide of where to look.”