Teen pregnancy is down 40% in Colorado, and the reason is unbelievably simple: birth control.

Over the past several years, teen pregnancies and abortions in Colorado have been on a sharp decline.

The New York Times highlighted the state's success story, in which the teen pregnancy rate dropped by 40% and abortion rate among teens dropped by an astounding 42%.

Data from Colorado Department of Public Health & Environment.

Why the sudden drop? It's simple, really: The state made long-acting birth control free to those who wanted it.

Since 2008, Colorado has enabled more than 30,000 individuals to obtain long-acting reversible contraceptives (LARCs), typically intrauterine devices (IUDs) thanks to a state program called the Colorado Family Planning Initiative.

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According to the Guttmacher Institute, IUDs are one of the most effective forms of reversible birth control, with a failure rate less than 1%.

It should come as no surprise that when you make extremely effective contraceptives available to women who don't currently want to have children, unplanned pregnancies and abortions decline.

Sounds like a win-win scenario for just about everyone in the political spectrum, right?

Whatever your opinion on abortion rights, I think most people would agree they'd rather not need one. By their very nature, unplanned pregnancies are, well, unplanned. In reducing the number of unintended pregnancies, this program was able to chip away at the number of women needing access to abortion services.

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But what about the cost of providing free birth control? There's some good news on that front, as well.

Fewer unplanned pregnancies also means fewer parents who aren't financially able to care for a child; as a result, the state and federal government actually save money as the number of people in need of aid programs declines. A Guttmacher study determined that for every dollar spent on family planning programs, the government saves $7.09 on other programs. Which means Colorado's program pays for itself and then some.

The state estimates that just between 2010 and 2012, anywhere between 4,300 and 9,700 unintended pregnancies were avoided, saving the state somewhere between $49 million and $111 million in Medicaid funds.

Making birth control accessible is just one way to reduce unintended pregnancies.

Colorado's program was effective, but it's not the only way proven to reduce unwanted pregnancies. One method that's been shown to reduce teen pregnancy and sexually-transmitted diseases is simply being armed with the knowledge that comes along with comprehensive sex education.

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Studies show that abstinence-only education is not an effective way to reduce teen pregnancy.

As of July 2015, just 18 states and the District of Columbia require that sex education courses provide information about contraception. 37 states require that these courses cover abstinence (with 25 of those states mandating that courses stress the importance of abstinence).

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Abstinence-only-until-marriage programs haven't been shown to drastically affect the age at which students become sexually active. In fact, studies show that students who only received abstinence sex education were more likely to not use contraceptives and were more likely to end up with unintended pregnancies and STDs.

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All things considered, preventing unintended pregnancies is simple.

It's as easy as arming people with knowledge (comprehensive sex ed) and resources (contraceptives) to stave off unintended pregnancies. As we've seen, denying these resources to teens and adults proves to have a much more painful, expensive social and financial cost. Reducing those pregnancies will take a mix of both knowledge and resources.

As Colorado waits to find out the fate of its wildly successful program, it's helpful to look back on how simple the solution can be and why it's worth investing money and effort toward an effective public good. We should all be able to get behind that idea.