Violence between rival drug cartels has transformed some Mexican cities along the U.S. border into virtual war zones where criminals act with impunity and the annual body count is in the thousands.

Following are some facts and figures about the violence compared to U.S. rates of drug-related homicide, which help underscore the scale of the carnage in Mexico.

- In 2008, 6,000 people died in drug violence in Mexico, according to President Felipe Calderon. This was almost double the 3,042 who died in drug-related violence in 2007.

- There are no direct U.S. comparisons with those years but the data that exists from 1987 to 2006 in America shows that even at its worst, U.S. drug violence over the last two decades has not been anywhere near the Mexican levels.

- In 2006 in the United States, 794 of the reported 14,990 homicides in the United States were narcotics related, according to the Federal Bureau of Investigation (FBI).

- U.S. drug-related homicide statistics have been compiled since 1987 and the peak year was 1989 when 1,402 or 7.4 percent of America's almost 19,000 murders were linked to narcotic activity. That is still only about a quarter of Mexico's estimated drug death toll last year and the U.S. population is about three times that of its southern neighbor.

- Much of the drug violence in Mexico is concentrated in a few cities near the U.S. border, the heart of the lucrative trade in drugs and people to the north, and weapons flowing to the south.

- Out of the 6,000 murders in Mexico's drug war last year, more than 2,000 were in the northern state of Chihuahua. Of these, an astonishing 1,600 took place in Ciudad Juarez, a city of 1.6 million on the Texas border.

- By way of contrast, El Paso, a Texan city of 600,000 just across the Rio Grande from Ciudad Juarez, had 16 murders in the first 11 months of 2008, according to the most recent data available.