I don't like to think of myself as a boomer, but I guess I am. And from my perspective, (born in 1963), I'd say my generation was spanked plenty! I can't remember a time growing up that I wasn't subject to spankings from my parents, teachers, camp counselors, adult babysitters, friends of my parents, the parents of my friends, etc., etc.! (not to say I got spanked by all of the above! Just that in those days they had that sort of authority). The last time my father whipped me I was 16 and almost as tall as he was.
Spanking was just in the air. I knew exactly one girl who wasn't spanked, and both of her parents were psychologists. Otherwise, the rest of us could be pretty much assured that if we misbehaved, or were disrespectful, or lied, or just got on the wrong side of a parent having a bad day that we could be punished. You saw it in on TV, you saw it school, and you saw it in your own home.
I know there was a wide gamut of how often, what age range, what implement, how severe. But if I take myself as an average late boomer, I got spanked more times then I can count (probably 2 times a week until I started school, and then maybe every week or two until I was 10, and then at least once a month from then until high school, at which point whippings were less frequent but more severe and applied maybe 3 times a year.