The best approximation we can get of the number of firearms sold each year comes from the FBI's data on gun background checks. In most cases, a person buying a gun is required to have a federal background check completed, and in 2015, the FBI conducted 23.1 million such checks.

That's more than 2 million more checks than in 2013, the previous annual record. We noted early last month that 2015 was on track to set a new record, but a huge December — bolstered by the holidays and almost certainly by fears of new gun regulations — put 2015 well into the lead. Since the FBI started conducting the checks in 1998, the December with the most gun background checks was 2012, in the wake of the massacre at Sandy Hook Elementary. That month, 2.78 million background checks were conducted. Last month, the number topped 3.3 million.

Which means that Barack Obama's certainly unwanted legacy of spurring a huge increase in the number of guns (to the tune of billions of dollars in sales) continues apace. In his second term, there have been 62.7 million background checks already, with a year still to go. That's a pace of nearly 1.8 million a month on average — compared to 720,000 per month in the first term of George W. Bush.

If 2016's background checks are anything like 2015's, Obama will close out his term having overseen nearly twice as many total background checks as Bush.

There's a catch. We noted above that the number of background checks was just an approximation of gun sales. Other things spur background checks, too. In Kentucky, for example, concealed carry permit holders have a check conducted every month, vastly inflating the number of checks from that state. FBI data show that in 2015, Kentucky alone accounted for 3.2 million checks — 1.5 million more than the much-more populous state of California.

Before 2006, Kentucky's background check counts were about in-line with Minnesota's. It was often a bit higher, but not always. If we assume that Kentucky's non-monthly checks track with Minnesota's, we can separate out all of those regular checks. The light blue bars below show our estimate of the number of additional background checks conducted in Kentucky relative to the overall total.

That's 17 million more background checks since 2006 than if Kentucky had continued to track with Minnesota. 2015 was probably still a record, but it's a lot closer to 2013 than it might at first have seemed.

Adjusting for Kentucky makes the surge in background checks under Obama look slightly smaller.

There's little doubt that the Obama presidency has prompted a big surge in gun ownership in the United States. But when the FBI states that "a one-to-one correlation cannot be made between a firearm background check and a firearm sale" on the bottom of every page of its data, it's worth taking that qualification to heart.