This is a good point. The average age of menopause in the US is, however, 51, not 40. That does not undermine your argument in principle, though. Probably, a w

This is a good point. The average age of menopause in the US is, however, 51, not 40. That does not undermine your argument in principle, though. Probably, a woman's chance of getting pregnant decreases the older she is, even if she is still menstruating. That would complicate the numbers but would not contradict your argument. This is why a province in China is offering a cash bonus to couples who marry before the woman is 25.