2017 saw the second-most gun-related FBI background checks on record, a report released on Wednesday showed.

The National Instant Criminal Background Check System (NICS) conducted 25,235,215 checks last year. That’s nearly 2.3 million checks fewer than the record-breaking year of 2016 but also nearly 2.1 million checks more than 2015, the third-best year on record.

The number of checks conducted by NICS is generally considered a leading indicator of how many gun sales have been processed in a given period of time in large part because nearly all sales—including all new gun sales—made through a federally licensed dealer must include a background check. It is not, however, a perfect representation of raw gun sales for a number of reasons. Sales between private parties on the used market are not required to go through a background check in most states. Sales of multiple guns during one transaction generally only require a single background check.

“These statistics represent the number of firearm background checks initiated through the NICS,” the FBI wrote in its report. “They do not represent the number of firearms sold. Based on varying state laws and purchase scenarios, a one-to-one correlation cannot be made between a firearm background check and a firearm sale.”

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