Ubiq: not necessarily. If we agree that the new generation has more kids than the one prior, the question becomes can we divide our population according to generations. In my community at least, mainly descending from Holocaust survivors, the dividing line used to be pretty obvious. Now the difference is less pronounced, but I believe the rule still holds true. If we can see the division, it becomes obvious that not all girls have a boy 4 years older, as 4 years older may mean a prior generation with presumably less boys.
So if (to simplify the numbers) we assume 20 childbearing years per couple, every 4 years is 1/5 of a generation. Now if our population is increasing by 100 percent every generation (again, to keep the math simple, a conservative average of 4 kids per family) each 4 year period would have roughly 20 percent less children than the following 4 years. That would mean 10 percent less older boys than girls with a 4 year differential in a span of 4 years. In real life the numbers don’t work exactly this way, as a 4 year period is also not stagnant and I’m underestimating, but I hope you get my point.
I’m not a mathematician, but I don’t think I’m being illogical. Please correct me if I’m wrong.