Homicide rates among teenagers and young adults have dropped to the lowest level in 30 years, according to the Centers for Disease Control and Prevention.
That's good news, but it still means about 4,800 young people under age 25 were murdered in 2010.
Teenagers and young adults remain more likely to be killed than older adults, and homicide is a leading cause of death in the young, behind motor vehicle accidents.
Homicide rates have dropped steadily since an uptick in the early 1990s, according to the CDC, which published the data today in Morbidity and Mortality Weekly Report. The homicide rate for people aged 10 to 24 was 7.5 per 100,000 in 2010, compared to 15.9 in 1993.
That mirrors a long decline in crime overall. There are plenty of theories for why that's happened, including better policing, higher incarceration rates, and the economic boom of the 1990s. But none of the theories have really been proved.
Indeed, scientists are at a bit of a loss to explain why we're seeing fewer murders and other crimes. "In short, we don't know," says Dr. Matthew Miller, an associate professor of health policy and management at the Harvard School of Public Health. "The usual suspects don't seem to explain it."
The legalization of abortion was at one point thought to account for it, but crime rates have dropped in other developed countries, such as Canada, that didn't change their abortion laws. Spending on policing has waxed and waned, but the decline in homicide rates, and crimes overall, has continued. The economy boomed, and then tanked. But homicides don't appear to have increased as a result.
One statistic hasn't changed: The death toll continues to fall disproportionately on young men, especially young black men. The homicide rate in 2010 was 12.7 per 100,000 for males, 13.2 for people ages 20 to 24, and 28.8 for blacks. "The disparities by race are extraordinary, and they're obscene," says Miller.
And some neighborhoods continue to pay a heavy price. The murder rate rose in Chicago in 2012, bucking the trend.
A broad variety of prevention programs aim to lower those numbers, including programs to help parents set rules and monitor children's behavior; school-based programs that teach techniques to solve conflicts without violence; and business-improvement districts to increase economic opportunities.
Better assessment is needed to find of which of the many programs really work best to prevent murders, Miller says, "but they're not easy."
And the CDC spends just $100,000 a year on research into gun violence, despite the fact that 79 percent of homicides in the CDC study were committed with firearms.
President Obama has pledged to increase funding for research on guns and violence, but it's unclear if his commitment reaches beyond a year.