Another week, another mass shooting in the United States. Barack Obama is furious at congress for its continual unwillingness to pass comprehensive gun control. Jeb Bush says “stuff happens”:

Once again the right is coming out with the same tired arguments, claiming that guns have nothing to do with gun violence, that mental illness is the culprit. This argument is facile and demonstrably wrong. I can show you why in four charts.

It’s true that the United States has the highest rates of mental illness and homicide in the developed world. But just because we are bad at both of these things does not necessarily mean that one causes the other. This chart compares the rates of mental illness to economic inequality:

We should notice two things:

Economic inequality has a remarkably strong relationship with mental illness–if mental illness were the cause of our gun problem, this would suggest that one of the best ways to combat the problem would be to reduce economic inequality. That’s a very left wing move. The right’s argument implies that we should all be supporting Bernie Sanders. The United Kingdom has the second highest rate of mental illness in the world.

Why does the UK’s mental illness rate matter? Because the UK has one of the lowest gun violence rates on the planet. Britain has less gun violence than many countries with significantly lower rates of mental illness, including Spain, Italy, Australia, Germany, France, and Canada. But do you know what Britain doesn’t have? Civilian gun ownership:

And it’s not as if those Brits are murdering people with knives–even if you look at the general homicide rate, Britain is a very safe place:

What we do see in both cases is a statistically significant relationship between the number of guns per capita and the gun violence and homicide rates. We can expand this analysis well beyond Britain–if mental illness were the primary cause of gun violence, we would expect to see a strong statistical relationship between the rate of mental illness and the homicide rate. Among developed countries, there is no such relationship:

Many countries have similar homicide rates despite completely different rates of mental illness. The US is just a couple of points less healthy than the UK or Australia, but it has a crazy high homicide rate. Belgium is much healthier than most countries, but its homicide rate is high by European standards. Italy has one of the lowest rates of mental illness around, but its homicide rate is nearly the same as New Zealand’s, which has one of the highest rates of mental illness. It’s time for conservatives to face facts–mental illness is not the core cause of gun violence or homicide–gun ownership is. And if this analysis is wrong, if mental illness somehow really is the cause? Then the research suggests that a big part of the problem must be economic inequality–which means they ought to vote for Sanders. It’s a no-win situation for conservatives.