That's highly misleading. The tweet conflates gun ownership with gun
counts. The chart largely illustrates the tiny percentage of gun hoarders
expanding their collections.
> Rates of personal and household gun ownership appear to have declined over the past decades – roughly two-thirds of Americans today say they live in a gun-free household. By contrast, in the late 1970s, the majority of Americans said they lived in a household with guns.
> But America’s gun super-owners, have amassed huge collections. Just 3% of American adults own a collective 133m firearms – half of America’s total gun stock. These owners have collections that range from eight to 140 guns, the 2015 study found. Their average collection: 17 guns each.
(See also the chart showing a couple percent increase in female gun ownership, but a fairly hefty decrease amongst men.)