Note the mistake of assuming preference = requirement. The whole everything that isn't forbidden is mandatory and everything that isn't mandatory is forbidden.<p>So search for a woman within age range X to Y, but I have never in my life carded a woman to make sure.<p>I might be wrong but the ancestry of the "rule" was some sort of statutory rape disqualification. Follow that rule as an adult in (insert state here) and it was a get out of jail free card for the guy even if the girl was technically underage. To handle those annoying "he's 18 and one day while and she's 17 and 11 months and 29 days old" situations. So technically you can't consent till you're 18, but if one partner is 18 and the other is 18/2+7 aka 16 or older, its not illegal. Needless to say this is not legal advice and I don't remember the state and it once being true in AL in 1920 doesn't mean its true today, anyway.<p>(and I'm getting downvoted. thanks guys. My point isn't that its great not to prosecute rapists or make a statement about some weird moral/ethical perspective on dating younger women or that I totally confused the article with some legal debate, but to point out that AFAIK this "common sense math formula" originally came from a statutory rape law in the American south decades ago, and thats the answer to the debate on HN of "where did this supposedly well known law come from that no one knows the source of" Perhaps given this as a start someone who knows the history of those laws, perhaps in the south, could confirm the details? I'm not asking you to agree with it, or promoting its reinstatement, just stating its history)