Considering the fact that I attended an evangelical university, I think my sample was highly skewed in the direction of at least 50% or more of couples waiting till marriage... and I was on the same bandwagon until I finally started thinking (or would that be feeling?) through things.
It blows me away, actually, how many of my formerly-close friends waited till their wedding night... and I know they did wait, believe me, because they were all repressed as hell. Looking back on it, I am glad that I didn't start having sex when I was too young to handle it, but I wish it hadn't come at the price of such psychological repression. I think there are a lot better ways of teaching healthy sexual habits to young adults without resorting to brainwashing (even though the brainwashers are equally brainwashed, hence the problem).
