Thanks for that, SoCal.
I'm not sure how the USA statistics compare to UK statistics, but probably about equivalent. Given the fact that one is in VMC a lot more than IMC, I'm not very surprised that's how they pan out. Very far from "almost all".
Incidentally, the UK Airprox Board state:-
About 10% of all Airprox are glider-related – that’s about 20 incidents a year. Almost all occur in Class G airspace which is of course for everyone to use. In such airspace, “see and avoid” is the primary means of collision avoidance.
From
Lessons Identified | UK Airprox Board