Would you believe that I can’t find a good answer for that? True. All these books and the whole wide internet, and all I can find is guesses. Seems no one’s interested in resaarching combo failure rates in vivo. So I’ll have to figure this out myself. Apologies if this is all wrong, but I’ll explain my thought process so we can figure out precisely how I’m an idiot.
With typical use, the condom failure rate is 21% - if 100 women have sex for one year using condoms as their contraceptive method, 21 of them will get pregnant. (So it’s not quite the same thing as saying that every time you have sex with a condom, you have a 21% chance of conceiving. Certainly most of the month, you have 0% chance of conceiving, since she’s not fertile. So all the condoms that fail were used during a minority of a woman’s cycle. I’m not sure how to work out the math there, but it makes it seem to me like the condom is a pretty crappy form of contraception, but it’s good for STI prevention, so we should be using them anyhow, right? ;))
Anyhow, so if we take that 21% of women who had the potential to get pregnant from the condom’s numbers, and now we point out that The Pill has a failure rate with typical use of 8%…oh dear, here’s where the math comes in. Multiply, right? 8% of those 21% could still get pregnant? 0.08 * 0.21=0.0168, or 1.68% So, in one year of sex, 2 out of 100 women who use both the condom and Pill will get pregnant.
Are 2% of Americans killed by drunk drivers every year? 13,846 people were killed in 2010 in “alcohol-related fatalities.” No good information as to what that means (does it include alcohol overdose? Falling off a ladder when you’re drunk? Drunk drivers killing themselves, or drunk drivers killing other people?), so let’s be generous and assume ALL of them were killed by drunk drivers. The 2010 Census found 308,745,538 people. So 0.0048% of Americans were killed in alcohol-related fatalities last year.
It’s far more likely that you’ll get pregnant or get someone pregnant, even if you use a condom and The Pill, than that you’ll be killed by a drunk driver.