In 2015, the FBI will likely process a record number of background checks for people looking to buy guns and get permits.

Background checks are a good proxy for measuring how gun sales are changing, even though one background check does not necessarily equal one gun. That said, the purpose of background checks has nothing to do with measuring sales. Rather, it is part of a 1993 gun control law called the Brady Act, which mandates that someone looking to buy a firearm from a dealer, manufacturer, or importer is subject to a criminal background check. As part of this law, the FBI runs what is called the National Instant Criminal Background Check System, which pings three databases to quickly figure out whether a prospective buyer has a criminal record.

In the first 11 months of this year, the bureau already processed 19.7 million background checks. This is more than every other year on record — by nearly 800,000. This number includes a record-breaking Black Friday, when a whopping 185,000 background checks were requested.

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But that might not be the only record set this year. Given past trends, it's also possible that this month will have more gun-related background checks than any month — ever.

It's trending upward. It's December. It's after a mass shooting.

Gun-related background checks have steadily been on the rise for the past 10 years, but it wasn't until Barack Obama won the 2008 presidential election that background checks skyrocketed. Many people in the US feared the Obama administration would push through stringent gun control laws while the Democrats controlled Congress. From 2007 to 2014, background checks almost doubled.

So the upward trend is already in place. What's more, December is almost always the peak time of year that people look to buy guns. In fact, if you look at the chart above, you can see a seasonal spike every year.

Given the upward trajectory of backgrounds checks, as well as it being December, it's not a stretch to think this will be one of the biggest months for gun sales ever.

There's also one other event in play: the recent, highly publicized mass shooting in San Bernardino, California. Historically, gun sales go up in the wake of these events, as a national conversation about gun control begins. After the the Sandy Hook shooting in December 2012, a record number of background checks were processed, and it took a few months for that number to regress back to the mean.

So it makes sense to expect a record number of background checks when New Year's comes around.

Handguns and permits are on the rise

We talk a lot about assault weapons, but according to background checks, long gun sales haven't changed that much over the past 20 years.

Rather, what's changed is the number of people looking to get a permit and the number looking to buy a handgun.

From 2007 to 2014, background checks for handguns and permits increased by 144 percent. In that same time span, long gun background checks increased by just 21 percent.

That said, long guns have always caused spikes around the holidays

Long guns aren't on the rise in the long term, but each year we see spikes in background checks for long guns around the holidays. The seasonal spikes for permits and handguns do exist, but they aren't as pronounced.

So if December is going to be a record month, it's probably going to be a combination of both a larger holiday spike in long gun sales and the continuing trend of more people seeking permits and looking to buy handguns.