If you're practicing the pull-out method with a teenage boy who's still learning how to maneuver his equipment and who has only recently gone through puberty, I'd say those risk percentages would likely be much higher. On the flip side, if a woman is aware of how her menstrual cycle works and familiar with her own body and how it presents at different times during her cycle--most efficiently and effectively understood by maintaining a regular practice of charting your cycle--then she's already likely aware of exactly when she's *likely* to be fertile and can thus make educated decisions about which level of contraception would be the most responsible one for her body at any given time. When charting over a long term, we start to see signs and notice symptoms that tip us off to what is happening in our bodies during different parts of our cycles... for example, learning about the consistency of your discharge, different moods you have at different stages of your cycle.. I found I was often getting mild back pain and cramping mid-cycle and after I'd been charting consistently for about a year, I realized that was always happening on or within a couple days of when I was likely to be ovulating.. and that's because I was! I've since learned that is a common sign of ovulation, called "mittelschmerz," and there are SO many other signs we can learn about to empower us to know when we're fertile. Also, if we are practicing the pull out method with a long term partner whom we know and trust, that would also lower that odds too, I would think.
Just an FYI for any nay-sayers...In the 20+ years I've been sexually active while ONLY practicing the pull out method of contraception, I've had exactly ZERO accidents. Not one.. and I've had a LOT of sex! I also became pregnant within 2 months when we did decide to conceive, so avoiding an unwanted pregnancy for 20 years with only my partner pulling out unlikely boils down to mere luck.
I can't recommend cycle charting enough, it's the most empowering thing a woman can do for herself health-wise. I bet cancer mortality rates among women in the US would bomb within a couple years if every woman began charting.. We are far more likely to detect something wrong much sooner if we are charting and paying attention to our bodies.