Last year, the media was touting a consistent narrative: the legalization of marijuana in a few U.S. states was likely leading to large drops in Mexico's violent crime rate.

At The Daily Caller from February 2015:

Homicides in Mexico have dropped from 22,852 in 2011 to 15,649 as of 2014, which tracks relatively closely with the legalization of marijuana in Colorado and Washington, although the link between the two events is not conclusive.

From Time magazine in April 2015:

Coinciding with legalization, violence has decreased in Mexico. Homicides hit a high in 2011, with Mexican police departments reporting almost 23,000 murders. Last year, they reported 15,649.

With the release of the full year of 2015 crime statistics from Mexico, the most likely conclusion appears to be that pot legalization in the U.S. had a minimal -- if not negligible -- impact on violent crime for its southern neighbor.

First off, credible journalism on the topic must acknowledge that Mexico's crime data is deeply flawed, a point which cannot be stressed enough. There is rampant evidence of either incompetence or political alteration (or, more likely, both) in its violent crime data. These concerns are well-established among experts from multiple security-oriented organizations who have been critically looking at the Mexican statistics.

In addition, any trends in Mexico's violent crime data must be interpreted within the context of what actions President Felipe Calderon's administration took during late 2006 through 2012, sending in the military against the cartels -- resulting in the official period of the so-called “Mexican Drug War.”

During this time frame, violent crime rates spiked upwards as the cartels retaliated. After Calderon left office, the war died down primarily because of a less aggressive role for the Mexican military under President Enrique Pena Nieto. With Pena Nieto, Mexico has essentially given up on efforts to seriously attack the cartels, which would naturally result in reduced violence. One could also reasonably question whether Pena Nieto's administration has altered the crime data to make his term in office appear more favorable than it actually is.

Accepting the Mexican crime data as is, flawed though they undoubtedly are, it is still clear that rates of homicide, kidnapping, and extortion remain well above their pre-2006/2007 levels, and the patterns of any subsequent declines from the drug war peaks are not consistent with a causal linkage to U.S. marijuana legalization.

Homicide rates started to decline after 2011, and have barely changed since 2013 -- which is the period where the bulk of the American drug legalization efforts have kicked in and accelerated. In fact, the homicide rate increased -- not decreased -- between 2014 and 2015, the opposite trend expected if legalization was a determining factor.

Kidnappings remain above 2008 levels, and more than twice what they were before the drug war.

Extortion rates were increasing prior to the drug war, and haven't shown any clear and consistent trend since 2008 -- having high interannual variability.

The long-term impacts of U.S. marijuana legalization efforts on Mexican crime rates are unclear, but one thing is certain: it is far too early to be ascribing any significant reductions in violent crimes (assuming they actually are declining) to legal pot.