HiPhil wrote:I wonder if 18600 people / square mile is already adjusted for little children and senior citizens, who are doubtful to have sex 80 times a year, for 30 minutes.
It shouldn't matter, since they're already counted in the average, aren't they?
(Also, LapseOfSanity, keep in mind that duration * frequency is basically the portion of your life you spend actively having sex, and for all the people there, a square mile is tens of millions of square meters, so you're going to get a pretty small denominator if you pull a reasonable distance unit outside. Remember, the figures given in the comic do work out to 150 m, more or less.)
And I imagine multiple-partner intercourse would work by using weighting it against the average as 2/n.