>I believe the base rate of people who never find a sexual relationship in their entire lives (assuming they want it) is miniscule. Some quick searching puts it at around 0.5% by age 40.

[1] puts it at 1.2%, which would be about two million American men.

[1] https://www.washingtontimes.com/news/2011/mar/3/government-s...

Edit: Arguably fairer to just divide by the number of over-40s in America, which would make it only about half a million.