The Zetas cartel has become the biggest drug gang in Mexico, overtaking its bitter rival, the Sinaloa cartel

A new report by geopolitical analysis firm Stratfor says that the Zetas now operate in more than half of all Mexican states. Stratfor says that the Zetas' brutal violence seems to have given the gang an advantage over the Sinaloa cartel, which prefers to bribe people. Since 2007, 47,500 people have died in drug-related violence in Mexico. The report says that drug-related violence in Mexico has persisted, despite the government's efforts to fight the cartels. The report's authors say that the violence has shifted, abating in some cities while worsening in others. It lists the cities of Veracruz, Monterrey, Matamoros and Durango as examples of places where violence has increased, while murders in Ciudad Juarez have dropped, although the city remains the most violent in Mexico. According to the study, most smaller drug gangs have been subsumed by either the Zetas or the Sinaloa cartel, turning the two groups into the predominant criminal forces in Mexico. The Zetas control much of eastern Mexico, while the Sinaloa cartel has its stronghold in the west of the country. The Zetas, whose leadership is composed of ex-special operations soldiers, resort to extreme violence. The Sinaloa cartel, although also ruthless, prefers to bribe and corrupt people, as well as providing intelligence on rivals to the authorities. The report forecasts a continued expansion of Mexico's cartels into South America, a strategy which eliminates middlemen and brings in more profit. Smuggling drugs into the United States is now more difficult as a result of increased violence in northern Mexico and more stringent law enforcement along the border, Stratfor says. The cartels have responded to this by trafficking more to alternative markets in Europe and Australia.