As others have pointed out, that's not really all that much more common. Another reason for it is I believe that Global Entry and Nexus both still have a blanket "no criminal convictions of any kind at any time" requirement... which rules out something like 25-30% of the US population. Precheck also has a criminal background check but it isn't immediately disqualifying in all cases.
Yeah, I think that was a general estimate I found some supporting research for a few years back when I looked into it a bit, and I've seen similar quoted elsewhere.
It's not easy to come up with an accurate number at all due to all the different state systems not being perfectly comparable, treating different things in different ways, and duplicating individuals who have convictions in more than one state. Even attempts to link them together have been incomplete and inaccurate.
I'm not particularly surprised at that level, though... it's going to include _lots_ of low-level things that are technically classified criminal even though they're often just a ticket: kids caught with beer at a party, speeding in areas that have a "20 over the limit" rule that automatically upgrades to a higher offense, failure to pay tickets that gets escalated to a court, etc...
https://www.sciencedirect.com/science/article/abs/pii/S00490...) suggest that in 2017, 8% of the US adult population had a felony conviction, 24% of Black adults, and 33% of Black males. But for TSA Pre/Global entry, the relevant number is the number of fliers, where I suspect the felony rates are lower.
