Murders are up across the country, according to new 2015 FBI data, and they spiked in Colorado too. But Colorado's murder rate remains lower than the nation's as a whole.

Put in a historical context, 2015's bump is also small compared to the crime waves of decades ago.

"The idea that Colorado is safer than the rest of the country is correct," said Scott Phillips, a criminologist at the University of Denver. "But even the rest of the country is safer than it used to be."

Seven large cities are responsible for the increase nationwide, NPR reports: 

Chicago, Baltimore, Houston, Milwaukee, Philadelphia, Kansas City and Washington, D.C. That pattern has not held steady into 2016, as homicides in some places, including Baltimore and Washington, D.C., have dropped.

Denver's 2015 murder rate -- 7.8 deaths per 100,000 people -- jumped slightly from 2014 and was much higher than the state's rate of 3.2. In terms of raw numbers, the city saw 51 murders last year -- a 10-year high. But the capital city's murder rate is less than half of what it was in the early 1990s.

Murders are still exceedingly rare, Phillips said. He advises taking any seemingly big gains with a grain of salt.

"It doesn't take much of an increase to seem like a big increase," he said.

The new FBI report also covers other violent crimes; rape, robbery, and aggravated assault rates all ticked up slightly in Colorado in 2015. Nationwide, those rates also rose last year over 2014.