They claim the number of gun owners is shrinking when my observation is the exact opposite. Lots of people I know have acquired guns who did not own them previously.
A friend of mine started me shooting 10 years ago, I had not been a gun owner.
Since then I have introduced at least 6 people to firearms ownership.
They also claim 265 million guns total. That underestimates by 140 million guns.
The low number of guns confirms that they are missing tens of millions of gun owners.
http://gunwatch.blogspot.com/2017/01/2016-record-year-for-nics-background.html
There have been 150 million guns added since 1999 alone.