I’m going to question the “most adults” part. At least assuming the OP is interested only in people who’ve been in publicly distributed naked vids. As distinct from private personal-use-only naked vids.
When did amateur porn become a thing? WAG 2005. What is the demographic that creates most amateur porn? WAG over age 18 and under age 35.
Going from those WAGs, almost everyone born before 1970 and many people born before 1987 are too old to have participated in this popular new hobby. That’s about one half the current US population, and 2/3rds of the over-18 population.
Of the rest, it’s still a tiny fraction. If we wag there’s 300 million Americans, then 100 million are in our porn-producing demographic. And more age into it every day. So that’s the denominator, the population of potential amateur porn actors.
What’s the numerator, the number of actual amateur porn actors? Good question. Let’s tackle it.
If one was an avid porn *watcher *one might spend 8 hours a day 365 days a year watching 5 minute shorts. That’s 365,000 vids per year. If you watched like that for 300 years you’d get up seeing around 100,000,000 vids. At which point you’d have seen a bunch of dupes unless every eligible person had acted in one.
My point being that a more realistic sample size for even an avid porn watcher is a couple thousand vids. 2000 5 minute vids is 10,000 minutes = 166 hours = 20 8-hour days. Or a half-year of 1 hour per evening watching. Good bet after that many you’ll be hard pressed to remember/recognize anyone.
And even if each vid really was two unique people, it’d only have taken 4000 people to make them all. 4,000/100,000,000 is 0.00004 = 0.004% = 1 in 25,000.
So your typical US suburban town of 50K people has one couple making porn. Do you know (or even recognize) everyone in your suburban town? Nope. Odds are you don’t know somebody who makes porn.
The odds might well go up 10 or 20x if you hang in *just *the right demographic of looks, attitude and “class”. But my 1:25,000 is already demographically filtered for age.