> That logic doesn't make any sense unless you assume there are 100 men to every woman on earth, or alternatively, that women have 100 times more sexual partner

> That logic doesn't make any sense unless you assume there are 100 men to every woman on earth, or alternatively, that women have 100 times more sexual partners than men. Evidence suggests otherwise. Even if men and women have the same number of sexual partners female birth control will be more efficient if that number is more than one. Consider a hypothetical group of 1000 men and 1000 women that consists of 500 monogamous couples, using no birth control and frequently having sex. If you randomly pick half the men and give them male birth control or randomly pick half the women and give them female birth control then you'll but the number of births approximately in half. For that group then male and female birth control are equally efficient. Consider a similar group, 1000 men and 1000 women, but without monogamous couples. Each person has a dozen partners they regularly have sex with. In that group giving 500 women birth control will cut the number of births in half. Giving 500 men birth control will lower the number of births some but not much. For that group female birth control is more efficient.