The number of U.S. homicides has been falling for two decades, but America has become no less violent. The Wall Street Journal says the reported number of people treated for gunshot attacks from 2001 to 2011 grew by nearly half. So more people in the U.S. are getting shot, but doctors have gotten better at patching them up. Improved medical care doesn't account for the entire decline in homicides but experts say it is a major factor.

Emergency-room physicians who treat victims of gunshot and knife attacks say more people survive because of the spread of hospital trauma centers—which specialize in treating severe injuries—the increased use of helicopters to ferry patients, better training of first-responders and lessons gleaned from the battlefields of Iraq and Afghanistan. "Our experience is we are saving many more people we didn't save even 10 years ago," said C. William Schwab, director of the Firearm and Injury Center at the University of Pennsylvania.