According the United States Government, there is one birth every 8 seconds in the USA (http://www.census.gov).
That's about 11,250 births per day.
So that is 11,250 couples having sex today, excluding couples where one partner or the other is sterile. Excluding all gay or lesbian couples, oral or anal sex acts, bestiality or other activities where there is no possibility of pregnancy. That's couples having sex today, where the result WILL be a child.
What is the percentage of the population that uses birth control? 10%? 90%? Let's say 75% use birth control and it is 100% effective, which is absurd, I can tell you from personal experience. So the 11,250 figure is produced by the 25% that do not use birth control. That means that 45,000 couples will have sex today, excluding all the groups I already mentioned.
We all know women have cycles, and are fertile for, what, a week or so? Let's say 50% of the time. So those 11,250 births are the result of 22,500 couples having sex at a fertile time of month, without using birth control. So instead of 45,000, the number is more like 22,500 plus that 75%, or 56,250 couples having sex today with some real chance of conceiving a child.
It takes about 9 months or so to pop one of those puppies out, and let's assume at least 3 months downtime after that. More, really, but let's say. So 11,250 couples times 365 per year, means that 4,106,250 additional couples are or were recently pregnant and thus could have sex without making babies. Somewhere I read that Americans have sex on average 3 times per week. Yeah right. I think it was in Cosmo, I'm sorry I can't remember exactly where. So fewer than 1/2 of those might have sex today, or about 2,000,000. Of course, people usually don't have sex as often when pregnant, so let's be brutal. Say 500,000 protected might have sex today. We're up to 556,250 couples, by the way.
We won't discuss the numbers where the baby was lost, because that saddens me.
Let's take that the other direction for a moment. Eight seconds per baby. That's one ejaculation that results in a baby. We know from our analysis that there are considerably more ejaculations than pregnancies. About 5 times as many, in fact. So there are five ejaculations in eight seconds, or about 37.5 ejaculations per minute. Nationwide. Let's call that one per two seconds, or 0.5 ejaculations per second.
Then there are the 545,000 couples that might be having sex that won't be having a baby today, for sure. That works out to about 6.3 ejaculations per second for a total of 6.8 ejaculations per second, grand total.
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