6 different initial classes at 5 different regionals, none of which had flow at that time. Classes varied in size from 3 to 45 pilots. Probably averaged around 20, so around 120 total. I think at all, the first day of class everybody introduces themselves and gives backgrounds. I'd say, from what I remember, 90-95% of the people had bachelor's degrees or better. I remember one 21-year-old girl (my sim partner when I upgraded) had an associate degree. A couple guys had some college or tech but never graduated. I remember 3 enlisted guys from the airforce and army who didn't have degrees but none of them made it through ground school. The 2 airforce guys did something at the airforce one hanger and the army ranger guy flew jumpers in a twin otter or something (no IFR experience).
Other than the girl who was my sim partner, I'd say that none of the pilots I've been it class with without 4-year degrees was great at studying. A couple people might have been lack of effort, but for most, it was just bad strategy of how to learn. But, even so, very few pilots are weeded out in ground school. The real make or break time is sim and in sim prior flying experience matters more than a degree. I've seen lawyers, accountants, etc who came from being flight instructors and part 91 stuff who couldn't advance past the first sim lesson.
On the line the few pilots I'd fly with without bachelor's degrees were old timers who started out very early with the company, usually when it was a part-135 operation or very early part-121 days.
I don't recall ever flying with warrant officer guys who didn't have bachelor degrees, but the guys who have the associate's combined with the right flight experience probably do just fine, (just like the girl who was my sim partner).
So, from my experience, I'd say that nowadays at least 90% of new regional pilots have 4-year degrees. I'd say that the pilots who successfully make it through training without 4-year degrees have at least successfully completed some college (and of course have good flying skills). I know of nobody without at least 2 years of college who made it through a ground school I attended and I never heard of anybody flying the line with less than 2 years of college unless they came out of a 135 operation that gave birth to the airline. I'm pretty sure all those guys are retired now.