Via David Hardy we have:
telephone surveys result in numbers that are significantly too low, as by an eighth to a tenth, even when the ownership is completely legal.
These were old studies (1990 and 1995) but let’s assuming they are still valid.
This is where gun ownership is legal and doesn’t count situations such as Chicago or D.C. where gun ownership is highly problematic. So lets go with the “low by an eighth” number or:
0.875 x OwnershipRate = ReportedRate
OwnershipRate = ReportedRate/0.875
OwnershipRate = 1.14286 x ReportedRate
The reported rate for 2014 is 34% so the true ownership rate is approximately 39%.