One year after a record-setting year of gun sales in 2016, American gun buyers are continuing the booming market for guns. At current rates, 2017 will likely be the second-best year for gun sales in history, only slightly behind 2016.

Using statistics from the Federal Bureau of Investigation’s (FBI) National Instant Criminal Background Check System (NICS), over 20 million background checks have been registered with the FBI this year for a purchase of one or more firearms. NICS checks are not a completely accurate number of all gun sales, as they do not include private firearms transactions, and a single NICS check can be used for the purchase of multiple firearms at once. But FBI NICS numbers are generally considered the best measure of gun buying trends for Americans nationwide.

With the recent mass shooting in Sutherland Springs, Texas, three out of five of the deadliest mass shooting events in U.S. history have occurred within the last 18 months. While they still account for only a tiny fraction of overall gun homicides in the United States, mass shootings are clearly following a trend of generally increasing numbers of victims as shooters adjust and refine their tactics.

2016’s record-setting numbers of firearms purchases have largely been attributed to fears over what appeared to be an inevitable Clinton Administration making good on its promise to roll back gun rights in the United States. Similar fears over the rollback of gun rights during the Obama years have often been cited as the reason for booming sales during that time as well. But with the surprise election of Donald Trump, gun sales have seen only a slight dip from last year, and are still outpacing every year on record before 2016.

When looking at FBI data since they started to be recorded in 1998, gun sales were relatively stagnant from 1998 to 2005. In 2006, gun sales began to increase steadily annually. That is also well before the meteoric rise of Barack Obama, and gun sales had nearly doubled before Obama had even taken office in 2009.

It’s possible fears of losing their second amendment rights are driving Americans to buy guns. It’s also possible that changing societal conditions are encouraging them to reevaluate why they should own a firearm. The Pew Research Center shows that Americans consistently rate personal protection as a primary reason to own a firearm, more so than any other reason like hunting or sport shooting. Like mass shootings, jihadist terrorism is now a regular feature of American life, with many Americans citing fears of terrorism as reason to own and carry a firearm.