More than 60 percent of the prisoners surveyed were serving sentences on drug offenses, including trafficking, consumption and possession. The report, compiled by the Centro de Investigacion y Docencia Economicas (CIDE), a Mexican think tank funded by the federal government, sampled 726 men and 95 women.

“Mexico is living through a prison boom not unlike that seen in the United States,” wrote Steven Dudley of InSight Crime, an investigative online outlet focusing on Latin America.“The reasons for this rise are many: The general public now reports more crimes; changes in the law set higher penalties for those crimes; and penal authorities have an increasing tendency to prolong prisoners' stays in jail for bad behavior.”

The report found that 80 percent of women in Mexican prisons were jailed for drug-related offenses, with the rest imprisoned for either kidnapping, homicide, weapons charges or involvement in organized crime....

Some experts argue that the report’s statistics are skewed because the survey was conducted only in Mexican federal prisons and not state or local jails..

“The biggest thing that jumped out to me is that this survey is just of the federal system,” said Christopher Wilson, a researcher at the Mexico Institute, a think tank in Washington D.C. “That eliminates a whole group of crimes that are at the state level: robberies, homicides, things like that.”

Wilson was taken aback by the low volume of low-level drug offenses that led to imprisonment, with almost 41 percent serving time for drug crimes being charged for transportation and about 39 percent being imprisoned for possession.