楼上那个计算数字的，有一个很明显的错误，CDC网站上说64.9%育龄女性用所有可能的避孕手段，而不是荷尔蒙类的： In 2015–2017, 64.9% of the 72.2 million women aged 15–49 in the United States were currently using contraception. The most common contraceptive methods currently used were female sterilization (18.6%), oral contraceptive pill (12.6%), long-acting reversible contraceptives (LARCs)(10.3%), and male condom (8.7%). 前三项加起来是40%左右。而且前三项的保护率并不是100%， 尤其是如果口服避孕药没有完全按时吃药的比例其实不小。你不能指望强奸犯强奸的时候还戴套吧？ https://www.cdc.gov/nchs/products/databriefs/db327.htm#:~:text=In%202015%E2%80%932017%2C%2064.9%25,and%20male%20condom%20(8.7%25).