Where are all the world's guns? If news headlines are anything to go by, arsenals seem most stacked in the United States. In the wake of mass attacks such as in Charleston, South Carolina, and the massacre in Orlando, gun ownership and control are among the most hotly debated issues in the country.

President Barack Obama, who described the Orlando attack as "an act of terror and an act of hate", has said the massacre was a further reminder of how easy it is for Americans to acquire a deadly weapon.

But not everyone is buying them: a survey by Harvard and Northeastern universities estimates that the 133 million guns in the US are concentrated in the hands of just 3% of American adults – a group of super-owners who have amassed an average of 17 guns each.

Where do people own the most guns?

The map shows private gun ownership levels around the world measured by the number of guns per 100 people.

 Private gun ownership levels around the world measured by the number of guns per 100 people
Image: Vox

The US has by far and away the highest levels – some 88.8 guns per 100 people in 2012. This figure is dropping slightly. The Harvard/Northeastern survey, reported by the Guardian, found that while America’s gun stock has increased by 70 million guns since 1994, the percentage of Americans who own guns has decreased from 25% to 22%.

After the US, the next closest country is Yemen, with 54.8 per 100 people. This translates into another remarkable statistic – 4.4% of the world’s population live in America, but 42% of civilian-owned guns across the world are found in the US.

Is there a relationship between gun ownership and gun violence?

The following charts suggest that yes, there is.

The first chart from Mother Jones, a US non-profit news outlet, shows gun ownership against gun violence in US states.

Gun ownership vs gun deaths by US states
Image: Mother Jones

Using 2013 data, the chart highlights that there is a correlation between gun ownership and gun deaths. Those states with higher levels of gun ownership do see more gun-related deaths.

This is a trend reflected across the developed world, as shown in the following chart from Tewksbury Lab, a division of the University of Washington.

 Guns deaths vs gun ownership
Image: Tewksbury Lab/University of Washington

As the red line of best fit indicates, as gun ownership increases, so do gun-related deaths. The US tops both these indicators in the chart.

The evidence therefore suggests that higher levels of gun ownership do lead to higher levels of gun violence. The gun homicide rate in the US is six times higher than in Canada, seven times higher than in Sweden, and nearly 16 times higher than in Germany.

Do stricter controls make a difference?

Economist Richard Florida has examined the link between gun deaths and other social indicators, and found that US states with stricter gun control laws have fewer gun-related deaths.

 Gun laws and gun-related deaths
Image: Martin Prosperity Institute

The evidence suggests that President Obama’s executive action, which bypasses Congress, could have a positive impact on gun violence in the US, and could be a step on the path towards preventing further mass shootings.

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