“Statistically, could someone please explain how 2.55 million background checks translates into 1.9 million firearms sold?”
To be precise the 1.9 million are firearms added to the existing stock. Background checks are also done for CCW permits, many are done for existing firearms that are sold on the used market.
The ration of checks to new stock is based on the NICS numbers of checks compared to the ATF reported number of guns manufactured for the private market, plus imports minus exports.
Excellent, thanks for the explanation!