As Enrique Peña Nieto takes the reins as Mexico’s president, optimists in the war on drugs argue that the worst is over regarding the violence that has convulsed his country over the past six years and left at least 60,000 dead. The centerpiece of that argument is the improved situation in Ciudad Juárez, directly across the border from El Paso. For several years, Juárez has been the epicenter of fighting between drug cartels, as well as between the cartels and the Mexican government. But in the first 10 months of 2012, homicides and kidnappings in the city dropped by more than 60 percent. Reuters correspondents Dave Graham and Julian Cardona note that Mayor Hector Marguia is bubbling with optimism. “It’s a completely different city now,” Marguia stated.

The dire security environment in Juárez has become somewhat less dire, but the overall picture in Mexico is far murkier. Even in other portions of Chihuahua, the state in which Ciudad Juárez is located, there has been little improvement. National police statistics show that property crime (including extortion) in Chihuahua is headed for its worst year in more than six years. And the decline in homicides in Juárez has not occurred in other regions wracked by drug-related violence. The situation remains extremely turbulent in places like Tamaulipas state (directly across the border from southeastern Texas) and in cities such as Monterrey, Mexico’s industrial heart.

As a lengthy special report in The Economist confirms, the pattern with respect to homicides on the national level offers no more than a glimmer of hope. After peaking in late 2010 with 2,000 killings a month, the rate has apparently reached a plateau. But the nature of that statistical plateau ought to sober even enthusiastic drug warriors. Although the rate is down seven percent during the first nine months of 2012 from the same period a year earlier, there are still nearly 1,800 victims per month. That is more than two and a half times the number when Felipe Calderón took office as president in December 2006.

Where violence has declined more extensively, as in Juárez, the reasons are not especially comforting. Joaquin “El Chapo” Guzman’s Sinaloa cartel appears to have finally defeated the Juárez cartel and other rivals. Having won the bloody, multi-year turf fight, the Sinaloa organization now has effective control over the lucrative trafficking routes through that area into the United States. Graham and Cardona cite Mexican consultant group Risk Evaluation’s assessment that the amount of cocaine and marijuana smuggled across the U.S.-Mexico border is up at least 20 percent since 2010 and methamphetamine shipments are up some 40 percent. Juárez businesses now routinely pay extortion fees to the Sinaloa cartel.

The subsiding of violence in Juárez follows a pattern that has occurred in a number of U.S. cities over the years. Homicides soar when two or more drug gangs battle for control of the market, and the killings decline either when one gang becomes dominant or the contenders reach an explicit or implicit market-sharing agreement. For example, homicides (mostly related to the drug trade) in Washington, D.C. peaked during the early and mid-1990s at more than 400 per year. The rate has plunged since then, and in all likelihood there will be barely 100 killings in 2012. That does not mean, however, that there has been anything remotely comparable to that decline in drug trafficking. Indeed, the illegal trade appears to be flourishing.

A similar pattern appears to be occurring in those areas of Mexico where the turf fights largely have been decided. But the resulting relatively quiescent periods are inherently precarious. They last only as long as a truce holds among competitors or until a new challenger arises to confront the incumbent dominant trafficking organization.

All of this suggests that optimism about improvements in Mexico’s security environment is overdone, or at least premature. Much depends on what policies Peña Nieto adopts toward the drug cartels. Even senior Mexican government officials contend that the gangs have been “biding their time” to see what the new president does on the issue.

Peña Nieto has given mixed signals about his intent. The tone of his inaugural address certainly was different from that adopted by his predecessor. Felipe Calderón always stressed the goal of smashing the cartels and achieving a definitive victory. Peña Nieto emphasized the need to “restore peace” to the country. Yet he did not repudiate Calderón’s confrontational, military-led offensive against the cartels. As with so many of his other policy views, Peña Nieto’s stance on the drug issue is translucent rather than transparent.

The underlying reality is that as long as drug prohibition remains the policy of the United States and other consumer nations, the vast black-market profit potential will lead to bloody turf fights between contending suppliers. And those organizations also will fight ferociously against any government that tries to interfere with their business. That has been the unpleasant situation in Mexico, especially during the Calderón era. Time will tell if Peña Nieto’s policies will reduce the confrontation and, hence, the extent of the killings. At the moment, though, there is nothing more definitive than a pause in the rise of violence. Drug-related homicides still occur at an alarmingly high level that poses a significant security problem for Mexico and its neighbors.