Labeling it as such doesn't make it more convincing.
And let's take a look at the study you provided. Pages 5-6. To start, this study consisted of 2,568 participants. They asked them where they got their guns. From those participants, roughly 60% of them said from "Stores". On top of that, they are estimating the total number of guns sold. Which they would still have no data on guns sold privately, other than what was answered from the 2500 participants. So the total number of sales is questionable. And they extrapolate the 60% results from the 2,500 participants, and applied that to the roughly 300 million total gun owners in the country. They admit in several places that their participants might be "misremembering" or they assumed
that the place they bought it from was a FFL. Yeah.
Here's a few highlights of their study:
Acquisitions. To date, little information has been available about gun flows in the United States. The potential importance of this information is its use in evaluating regulation of firearms commerce. For example, the Gun Control Act of 1968 restricts interstate shipments to federally licensed firearm dealers (FFLs), who in turn are required to follow laws regulating retail transfers. Transactions not involving FFLs, known as the "secondary market," typically do not require recordkeeping and are exempt from the Federal requirement (for handguns) of a waiting period and criminal record check.
Moreover, secondary market transactions are not subject to regulatory oversight. Thus, knowing the volume of informal transfers that do or do not involve FFLs would be useful.
The predominant sources of guns, unsurprisingly, were stores (60 percent). Other important sources included family members and acquaintances. The 3 percent of respondents who indicated that they obtained guns "through the mail" (which is illegal for all but FFLs) may have misremembered or may have referred to a mail-order purchase arranged through an FFL.
The average gun obtained in 1993 and 1994 was worth $392 at the time of transfer, with little difference between handguns and long guns. Fewer than 1 in 20 guns acquired during those 2 years were valued at less than $100. Fifty-seven percent of firearms were obtained from stores, pawnshops, or other sources that the respondents were certain to have been federally licensed firearm dealers. Some respondents were not sure about whether the source was an FFL. Others indicated that the source was an FFL but then reported that the transaction was a trade rather than a cash sale or that the source was an acquaintance or family member. If those cases are included, the proportion increases to 64 percent.
We conclude that approximately 60 percent of gun acquisitions involved
an FFL and hence were subject to Federal regulations on such matters as
out-of-State sales, criminal history checks, and recordkeeping.