[6t6t6]

> Someone who uses a condom perfectly, each time, every time, still has a 50% lifetime (35 year) chance of having a child.

That statement makes no sense. If the condom is not broken or slips off, there's no chance that a woman is inseminated. Unless the man has magic sperms that can teletransport themselves into a woman's womb.

[kale]

Check this out: http://www.nytimes.com/interactive/2014/09/14/sunday-review/...

Perfect use of male condom: 18% chance of conception after 10 years. Typical usage: 86% chance of conception after 10 years.

Even "the pill": 3% chance at conception after 10 years with perfect use. 61% chance of conception with typical usage.

Everyone thinks they use contraception correctly. It may be true for anyone reading this forum, but if you're looking at policy, you have to account for typical usage. Education campaigns can move "typical" closer to "perfect" usage, but IUDs and sterilization are pretty much the only types of birth control that offer more than 50% chance of not conceiving in 10 years.

[ars]

Perfect use for condoms has a 2% failure rate. Perfect use means the user did nothing wrong, not that the condom was perfect.

0.98 ^ 35 = 0.49, i.e. 51% chance of failure.

Failure here means child conceived. And keep in mind that there is only approximately a 2% chance of having a child from each encounter, so condoms fail a LOT. (20% chance of a child if done at the right time divided by 3 days out of 30 where it's possible.)

Note that the low 2% conception chance is mitigated by looking at a failure rate over a full year, i.e. multiply 2% by the number of encounters in a year.