In my last post, I said that a wife should be willing to sleep with her husband once a month, and that this would fulfill the marriage debt. Since I know that some of you plan your private lives around my advice, I’ve decided I owe it to you to do more than just pull a number out of the air. Here’s why once a month is about right.
Suppose we want an average woman to have 3 children. Ask.com tells me that the median marriage age for American women is around 25, and the probability of becoming pregnant from one sex act is around 5%. Let’s say the woman stops having children at around 40. That’s 15 child-bearing years; however, we must excuse the woman for the roughly two years covering her pregnancy and the child’s infancy, so we’re really left with 9 years to get pregnant three times, i.e. 3 years to get pregnant once. Let’s say the couple has sex at time intervals dt, so that in 3 years, they have sex n=3/dt times. The probability of not being pregnant in 3 years is (1-p)^n, where p=0.05. Say we want to make this probability to be something moderately low, say 20%. Then a trivial calculation gives
dt = 3 log(1-p)/log(0.2) = 0.096 = about 10 times per year
So my “once a month” rule of thumb is about right.
Filed under: Forgotten Virtues, Gender roles, Sex | 3 Comments »
