That was my thought. I think it may have something to do with over-population. Or perhaps, with modern indoor heating and warm clothing (especially briefs), our vital equipment is simply too warm to produce high counts.
My guess is that it has to do with the unique English notion that a man pursuing a woman is an insult to the woman and uncivilized. Too bad Americans caught onto the idea and we get a bipolar cross of male-female relations in the good ol' USA. Between the homosexual-feminist jackboots on the left and the Bill Gothard legalites on the right, it is no wonder that we rely on unchecked immigration to grow the population.