Researchers in the United States claim to have established a convincing statistical link between gun ownership and homicide, according to a new study. The study, which appears in the American Journal of Public Health, challenges the National Rifle Association's claim that increased gun ownership does not lead to higher levels of gun violence. In the absence of state-level data on household gun ownership, the study used a proxy variable -- the percentage of a state's suicides committed with a firearm -- that has been validated in previous research. The study, led by Boston University community health sciences professor Michael Siegel,...