From South Carolina this week, America got another reminder: the US has more guns — and more gun violence — than any other developed country. Mass shootings in the United States are on the increase—from one every 200 days two years ago to one every 64 days now. This week's massacre of nine people in Charleston will boost those statistics. Yet, while mass shootings are dramatic, they only account for a small percentage of gun deaths and injuries -- in a country with more than 300 million guns in civilian hands. Gun control is politically impossible, but so-called "smart gun" technology may offer a way to make weapons safer. Advocates say they can only be fired by their owners, not by thieves, children or family members bent on suicide. But efforts to get them to market are being met with threats, boycotts and warnings that "smart guns" will mean government limits on gun rights.