1.7 million felons and mentally disturbed people have been denied a firearm purchase by the National Instant Check System (NICS) since 1999 (the latest Democratic talking point) you should know this.
Of those 1.7 million people who were denied a purchase through the NICS 96% were temporary denials.
In other words, 1 million, 632 thousand of them were able to buy their firearms a bit later. 1 million, 632 thousand of them were false positives, denied for a variety of reasons including having a similar name to a prohibited person.
That leaves 68,000 actual denials in thirteen years, about 5,000 a year. Does that mean that 68,000 felons were denied firearms sales? Well, we don't actually know that since we don't know why they were denied.
We also know that almost none of them were prosecuted. Since it's a felony to attempt to purchase a firearm if you are a prohibited person, we have to assume that many of them didn't realize they were prohibited until they were denied. (You'd be surprised how many people don't realize that the the domestic violence conviction that they pleaded guilty to in 1972 at age eighteen when they got into a fight with their wife now makes them ineligible to own a firearm). Many district attorneys presumably don't bother to file charges in cases where the prohibition dates back so many years.
Finally, from a financial standpoint, is the background check system an effective use of our money. Those 1.7 million denials cost buyers 4.25 million dollars. The system overall has processed 140 million applications, at $25 a head, cost consumers $3.5 billion.
So, to extend the calculation just a bit, $3.5 billion/68,000 denials, that works out to $50,000 per denial.
Even assuming that each of those denials were actual felons attempting to buy a gun, that seems like an inefficient use of resources.