States with the largest increases in gun ownership also have the largest declines in violent crimes, according to economist John Lott.

After studying more than a decade and a half of FBI data, Lott concluded that states with "concealed-carry" laws were safer than those which don't. While these laws vary somewhat from state to state, they generally allow adults without a criminal record or a history of severe mental illness to carry a concealed handgun.

• The violent crime rate is 81 percent higher in states that do not have concealed-carry laws that in those that do.

• Robbery is 105 percent higher and murder is 86 percent higher where law-abiding citizens are denied the right to carry a concealed gun.

• Among other crimes, assault is 82 percent higher, and rape is 25 percent higher.

• Between 1977 and 1994, for each year a concealed-carry law was in place, murder rates dropped 3 percent on average, with robberies and rapes each down 2 percent -- demonstrating that the longer the law is in place, the more effective it is.

Lott found that a passive victim is more likely to be seriously injured than one who resists with a gun. His findings are detailed in his new book, More Guns, Less Crime: Understanding Crime and Gun Control Laws.