A total of 76 law enforcement officers died in the line of duty in 2013, the FBI reported Monday . Of those, 49 died in accidents and 27 were killed as a result of felonious acts -- the lowest such figure in more than 50 years of FBI reporting , dating back to at least 1961.

The 27 deaths of officers as a result of criminal acts in 2013 were a significant reduction from 2012, when 49 officers were feloniously killed, as well as from 2011, when 72 officers were killed by assailants in the line of duty.

Following the Ferguson, Missouri, killing of Michael Brown, an unarmed 18-year-old, by Officer Darren Wilson in August, law enforcement advocates touted the regular and often life-threatening dangers officers face on the job. But the Bureau of Labor Statistics list of the 10 most-dangerous professions doesn't include law enforcement officer. The BLS said law enforcement accounted for 2 percent of total U.S. fatal on-the-job injuries in 2013, with 31 percent of those injuries caused by homicide.

Other studies on the deaths of officers in the line of duty also showed police were far less likely to be killed in 2013 than they had been in decades. According to a count by the Officer Down Memorial Page , which collects data on line-of-duty incidents, there were far fewer deaths last year than in more than 40 years.

A 2013 tally by the National Law Enforcement Memorial Fund showed 100 officers died in the line of duty last year, the fewest since 1944. Traffic-related fatalities were the leading cause of officer deaths in 2013. The report found that "firearms-related fatalities reached a 126-year low ... with 31 officers shot and killed, the lowest since 1887 when 27 officers were shot and killed."

The FBI data from 2013 said 26 officers were killed by firearms. The discrepancy is likely because the FBI's Uniform Crime Reports on Law Enforcement Officers Killed and Assaulted relies on incident reports from police agencies. The Officer Down Memorial Page and the National Law Enforcement Memorial Fund are independent non-profit organizations that conduct their own counts. National Law Enforcement Memorial Fund data on police fatalities in 2014 shows total police fatalities are up this year from last, though details aren't yet tallied.

While reports by the FBI and other groups give a good idea of how many officers are killed in the line of duty each year, the number of people killed by officers is far less certain. The unrest in Ferguson reminded the nation that there is no federal database or reporting standard to track of the number of justifiable homicides -- or even total people killed -- by police each year.

Activists have tried to mount independent campaigns to track these so-called officer-involved killings, but so far have been unable to create anything resembling a comprehensive list. Statewide efforts have seen slightly more success. In Utah, for example, the Salt Lake City Tribune recently reported that police in the state were the second-leading cause of homicide from 2010 to October 2014. Over that period, officers were responsible for more of the state's homicides than gang members, drug dealers or child abusers.

Many law enforcement agencies do report "justifiable homicides" to the FBI. A recently released report on these incidents in 2013 found that officers fatally shot 461 felony suspects last year, the most in two decades. Some experts have cautioned that this offers a very incomplete picture of the total number of civilians who die at the hands of police.