How bad is crime in the National Park System? That question comes up every year, and it gained heightened attention earlier this year when U.S. Sen. Tom Coburn claimed that murders had greatly declined thanks to legislation that allows park visitors to carry firearms with them.

The National Park Service's official crime stats from last year show that murders declined to just six cases in 2012 from nine in 2011 and 15 in 2010. The agency also reports that rape cases dropped a bit, to 28 last year from 34 in 2011.

However, the number of reported robberies increased to 65 in 2012 from 58 the year before; aggravated assault cases rose to 250 from 224; burglaries reached 349, up from 292; and reported larcenies or thefts reached nearly 2,800 cases in 2012, up from 2161 the year before.

Overall, the number of Part I offenses, which include murders, rapes, robberies, motor vehicle thefts, arsons, and aggravated assaults, stood at 3,657 and 2012, an increase of more than 700 cases from the year before.

Part II offenses, which include such crimes as fraud, vandalism, weapons charges, sex offenses, driving while intoxicated, liquor law violations, and gambling, dropped by more than 7,000 in 2012, down to 105,284, from 112,675.

When looking at crime statistics from the National Park System dating to 1995 it is hard to pinpoint any trends. Murders in the national parks have fluctuated from 16 in 1995 to 17 in 2005, down to four in 2009, back up to 15 in 2010, and down to six last year. Aggravated assaults have ranged from a high of 368 in 1998 down to 206 in 2009 before climbing to 250 last year.

One statistic that does jump out is the number of curfew and/or runaway cases reported to the Park Service in 2012. According to the agency, there were 1,605 such cases in 2012, an increase of more than 1,200 from 2011 and the highest number recorded over the past 17 years.

Park Service officials don’t try to interpret cause-and-effect for rises or decreases in crime statistics, and so it's difficult to say what's behind the rises and falls in various categories.