A police officer in Medellin, Colombia

By one watchdog's count, about 86 percent of the world's most violent cities are based in Latin America, a phenomenon that has remained constant for the past four years.

According to the non-governmental organization Mexican Citizens' Council for Public Security and Criminal Justice (or the CCSP-JP by its Spanish acronym), the world's most violent cities are predominantly found in Latin America. (The NGO explains its sources and methodology for calculating each city's homicide rate in a report accompanying the list.) 

The CCSP-JP has released this list every year since 2011, and comparing them helps illustrate a few interesting trends regarding homicide rates in the region. 

1) The concentration of violent cities in Brazil

The number of Brazilian cities violent enough to be placed among the 50 most violent in the world just keeps going up, from 14 cities on the list in 2011, to 19 cities in 2014. In 2011, just two Brazilian cities were among the world's ten most violent; that number has since doubled. One of those cities, João Pessoa, the capital of northern state Paraiba, has seen a particularly dramatic jump in violence over the years -- ranking 29th in 2011, and now ranking fourth. 

2) Steady improvements in Mexico

Since 2011, when Mexico had 12 cities that ranked among the world's 50 most violent, that number has now dropped to 10. Nine of those cities were among the 25 most violent in the world in 2011; now, there are only two -- Acapulco and Culiacan. 

3) Venezuela versus the US

Over the years, there hasn't been that much difference between the number of Venezuelan cities on the list, versus the number of cities in the United States. This year, both Venezuela and the US have four cities among the 50 most violent, but three of those Venezuelan cities are in the top 20, and just one is in the US. 

4) The 'miracle' cities  

Juarez had a staggering 148 homicides per 100,000 people in 2011, the second most violent city in the world. Now, it's the 27th -- with a homicide rate of 40. Torreon and Chihuahua saw similar improvements -- the homicide rate in these cities fell from 88 and 83, respectively, in 2011, to 28 and 33 in 2014. 

Meanwhile, Colombia's second-largest city, Medellin, is now safer than every other US city on this list -- Baltimore, New Orleans, St. Louis and Detroit. This is compared to 2011, when Medellin ranked at 14th.

However, as reported by InSight Crime, these improvements in Medellin may have less to do with government initiatives and more to do with an ongoing pax mafioso. Likewise, while the Mexican government remains keen on emphasizing the improvements in Juarez, the reasons behind the border city's declining homicides are a mixed bag.  

Another dramatic improvement was seen in San Juan, Puerto Rico, the 25th most violent city in the world in 2011. This year, it doesn't even rank in the top 50, an improvement that's been attributed to several policies, including more effective use of technology. Another city in the Caribbean, Kingston, remains among the top 30 most violent in the world, but saw a sizable drop in its homicide rate between 2013 and 2014, possibly helped by fewer police killings

On the flip side, one of the most dramatic upticks in violence was in Valencia, Venezuela. The city wasn't even ranked in 2011, then ranked 50th in 2013, with a homicide rate of 30 per 100,000. This year, it's the seventh most violent city in the world, with a homicide rate of 71. 

5) The effect of the gang truce in El Salvador 

After El Salvador negotiated a truce between its most violent gangs, its capital, San Salvador, went from the 20th most violent city in the world (in 2011) to the 44th, in 2012. After the gang truce fell apart, the city now has a higher homicide rate than it did the year before the truce -- it's currently the 13th most violent in the world.  

6) The degree of violence in Latin America 

It's not just the number of Latin American cities on the CCSP-JP's list, it's the degree of the violence found there. Of the 43 Latin American cities on the 2014 list, about 40 percent of them have homicide rates higher than 50 per 100,000, and about 46 percent have homicide rates at 30 per 100,000 or higher. The global homicide average is about 7 per 100,000.

7) Watch your back in San Pedro de Sula

It's been the world's most violent city four years running.