A trader on the floor of the New York Stock Exchange looks at stocks during the final minutes of trading on May 6. The Dow fell more than 600 points in a few minutes in what became known as the "flash crash."
Timothy A. Clary/AFP/Getty Images
The number of people killed on American roads has fallen by more than 20 percent in recent years, according to a new study. But motorcycle deaths are up. That may be because older drivers are buying motorcycles.