According to internet lore, there's a mathematical equation that governs the lower bound for the socially acceptable age of a potential dating partner: half your age plus 7, or, in mathematical terms, if x is your age then the lower bound is f(x) = x/2 + 7.
Seems simple, right? if you're 20, then the minimum socially acceptable age for a date is 17. But it was The Ragbag who pointed out that this rule has a duality: for the date to be socially acceptable, the rule must be adhered to by your date as well. In other words, there's a socially acceptable maximum too, given by inverting the equation:
It was only yesterday that i realised that the rule of thumb for dating people of different ages (the “half your age plus 7” rule) determines not only the lower bounds for dating but the upper bounds as well—that for each ½x + 7, there is a corresponding 2(x-7). For the last 15 years of my life, i have been ignoring an entire market segment, namely those of the genus cougar.
The Ragbag handily plotted out the socially acceptable upper and lower bounds for dates at various ages in the chart below:
Notably, the chart also implies that there is a socially acceptable lower bound for your own age: below the age of 14, by this rule, you shouldn't be dating at all.
Incidentally, if you're wondering how well is this rule adhered to in practice, the dating website okcupid.com has done an extensive analysis of age preferences amongst their members. A really interesting analysis (and quite sophisticated - maybe done in R?), especially for heterosexual males looking for the ideal age-ranges for potential dates.
The Ragbag: The half your age plus 7 rule