Last week, New York Times columnist Nicholas Kristof wrote a great op-ed, in which he eloquently described teen pregnancy as the problematic consequence of irresponsible adults, not hormone-addled teens. As someone who has spent my career trying to make educators, parents, and policy makers understand that teens are not the problem—we adults are—I loved the sentiment and applaud his effort to advocate for rational programs and policies. I was disappointed, however, with his use of a statistic that inaccurately describes condom efficacy as cumulative: It is misleading and potentially dangerous to suggest that someone who uses condoms as birth control for years will inevitably get pregnant.

He wrote:

Condoms are 82 percent effective at preventing pregnancy in any one year according to the C.D.C., but that means that after four years of relying only on condoms, most women will have become pregnant at least once.

When used consistently and correctly, condoms are 98 percent effective. But it is true that with “typical use,” condoms are considered 82 percent effective at preventing pregnancy. Put another way, 18 out of 100 couples who use condoms as their primary method of birth control will likely experience an unintended pregnancy in the first year of use.

Condom efficacy rates, however, are not a matter of simple probability. My chance of winning the lottery with a single ticket is about one in 150 million, so it stands to reason that if I buy 150 million tickets, I’ll win eventually. The same math can’t be done here. Success or failure does not happen by chance with contraception. It’s not like a roll of the dice, spin of the wheel, or purchase of a lottery ticket. It is completely within the user’s control.

When the rates are calculated, they include any couple that report condoms as their primary method of contraception in a given month—no matter how frequently or infrequently they used condoms that month. The 18 couples who experienced an unintended pregnancy during the first year includes couples who were using condoms incorrectly and couples who weren’t using them at all the day they became pregnant. We can all agree that a condom can’t work if it’s left in the night table drawer or never leaves the pharmacy shelf.

Additionally, it is important to note that this statistic is based on the first year of use, not any single year. There is no available data on users in their second year of using condoms—or their third or fourth year, for that matter. Researchers believe, though, that the numbers get better as the years go by, if for no other reason than that people who didn’t effectively use condoms either get pregnant or change methods.

James Trussell, a professor at Princeton University and an expert in calculating contraception efficacy, told me via email that calculations like Kristof’s “assume that the failure rate during typical use is constant over time. This assumption is not true, because the least adherent fail early, leaving behind a group increasingly comprised of the most adherent.”

This may make the efficacy rates confusing. Ultimately, though, it’s good news: It means that couples who are committed to staying pregnancy-free can improve their condom efficacy by using one correctly (which is not hard to do) every single time they have sex.

In an article for Rewire this past summer, I pointed out that condoms have taken a lot of abuse lately. Messages in the media have suggested they break easily, don’t protect against pregnancy, and take all the fun out of sex.

I argued that with such negativity swirling around this important prevention method, we should not be surprised that condom use among teens is down. And, like Kristof of the New York Times, I said that it was up to us adults to turn around that trend.

The first step, then, is to make sure all the information we put out about condoms is accurate and easy to understand. Teens who use condoms the first time they have sex are more likely to continue using them as they get older. In turn, this encourages lifetime sexual heath; condoms both prevent pregnancy and are the only way sexually active individuals can protect themselves from sexually transmitted infections (STI).

This is not to say that condoms are the best method for all young people, or that young women should not be encouraged to use methods such as IUDs and implants, which take the possibility of user error out of the equation. But condoms are easy to get, inexpensive, and do not require a visit to a health-care provider, so many young people rely on them, particularly when they first become sexually active. Teens—and all sexually active people—need to know that condoms are still a good option for preventing pregnancy in the first year or the fourth.