What percentage of american women over ages 18-30 are on birth control?

I have been on birth control off and on since i was sixteen. That doesn't mean i'm promiscuous, just cautious. I have two children, and right now that's all i want. Besides, don't tell me if they made a pill for guys to not be able to make babies with no long term side effects that 99 percent of men wouldn't take it... its a totally ist and way too personal question to ask anyone at a bar or any other social scene. your really very rude to ask it of girls you barely know, and then to judge them because of it is totally self righteous and hypocritical.