Gun deaths in the United States can be slashed by over 90 percent through universal application of laws requiring background checks of buyers and easy tracing of every bullet fired, researchers said Thursday.
Conducting a background check on every single gun buyer could more than halve the national gun death rate from 10.35 to 4.46 per 100,000 people, said a paper in The Lancet medical journal.
Background checks for all ammunition purchases would cut the rate to 1.99 per 100,000 people, and "firearm identification" to 1.18 per 100,000.
Firearm identification requirements oblige manufacturers to store images of the unique markings that every gun makes on the bullets it fires, for cartridges at crime scenes to be easily traced to the gun that fired them, and hence its owner.
"Federal implementation of all three laws could reduce national overall gun deaths to 0.16 per 100,000," said a press statement by The Lancet -- a drop of over 90 percent cut.
The study authors quoted statistics showing that more than 90 people are killed by guns in the United States every day -- some 31,672 in 2010 alone.
A man fills out his Federal background check paperwork as he purchases a handgun at the K&W Gunworks store on January 5, 2016 in Delray Beach, Florida.
"Firearm violence in the USA is an issue of substantial public health concern," they wrote.
"Mortality due to firearms is endemic, characterised by stable but high national fatality rates since 2000."
Just Wednesday, five people were shot dead and three hurt at a backyard barbeque in Pennsylvania, in a country where such slayings have become commonplace.
But death rates differ between states, as do gun control laws.
Overall, about 40 percent of gun sales are estimated to be "private transactions" that do not require background checks, said the research team from the United States and Switzerland.
They had made a statistical comparison between firearm-related deaths per US state, and differences in state gun laws.
They also looked at data on gun ownership per state, non-firearm murder rates and unemployment numbers.
Of 25 laws assessed, only nine were found to correlate with fewer gun deaths, the team found, and three much more strongly than the rest.
They then calculated the likely outcome if all US states implemented these three laws -- background checks for buyers of guns, for buyers of ammunition, and firearm identification.
"Background checks keep guns and ammunition away from those who should not be having them," study co-author Bindu Kalesan from the Boston University School of Medicine told AFP.
Handguns are displayed at the Smith & Wesson booth at the 2016 National Shooting Sports Foundation's Shooting, Hunting, Outdoor Trade show at anuary 19, 2016 in Las Vegas, Nevada.
"Fewer guns mean fewer homicides and fewer suicides," said Kalesan.
The study claimed to be the first to examine the impact of different laws on gun deaths.
"The findings suggest that very few of the existing state gun control laws actually reduce gun deaths, highlighting the importance of focusing on relevant and effective gun legislation," said Kalesan.
But the authors conceded that once laws are implemented, they could take "many years" to start having the desired effect.
Commenting on the study, David Hemenway of the Harvard School of Public Health said the authors had failed to calculate the potential impact of factors like poverty, alcohol consumption and mental health.
And the study was unable to examine actual changes in gun deaths before and after the passing of any given law.
"Most suggestive is their finding that the two laws currently receiving the most political attention in the USA -- universal background checks for both guns and ammunition -- seem to have the greatest effect on firearm deaths," Hemenway said.
"Although not the final word, the study by Kalesan and colleagues is a step in the right direction of trying to bring more scientific evidence to bear on the types of policies that could be most effective in reducing the serious gun-violence problem in the USA."