Not only that, but the background checks are the NICS system which is only being used in 26 states last time I checked.
NICS checks are used by all 50 states since ALL FFL dealers have to use it.
But in states where there is a firearm permit, the NICS check is only run once when the permit is acquired and not per gun purchase.
And in states where a concealed carry permit suffices for a NICS check, there is no NICS check for each gun purchase.
So those numbers are significantly low.. how many concealed carry people are there now compared to 8 years ago? And how many concealed carry permit holders have bought only 1 firearm in the last 8 years?
That also doesn't cover used gun sales in the majority of states which don't required FFL transfer for private sales.