Originally Posted by Libertine

How many people do you know who use the withdrawal method as a sole means of providing pregnancy, and for how long have they been using it?

The numbers indicate chances of not getting pregnant while in a relationship with regular sex over the course of a year.

So, chances of not getting pregnant using this method while assuming the average reported effectiveness rate (77%) over the course of 3 years would be (.77^3)*100=45%. (compared to about 70-80% for condoms, 90-98% for the pill, >98% for pill+condom and <1% for internal ejactulation - all assuming two fertile partners between the ages of 18 and 30)

45% chance of not getting pregnant over the course of 3 years isn't exactly good, but it's not something you'd be unlikely to encounter either.

Edit - And that being said, don't trust Google.