It’s so rare to read about good news in social policy that it’s easy to forget it ever happens. And yet, a 2012 report released to the public last month by the Centers for Disease Control (CDC) showed that the national teen pregnancy rate has fallen once again, continuing a decline that began about twenty years ago. Of course, the devil is in the details, and some bad news persists: rates continue to look dramatically different for different states and ethnic groups. Moreover, there is little consensus on what prevention efforts actually work, and even some programs (e.g. abstinence-only education programs) proven to have no effect have been stubbornly continued by many conservative states.

Overall, among fifteen to nineteen year-olds, the U.S. birth rate dropped by half between 1990 and 2011, falling from sixty-two to thirty-one births per thousand females. This decrease is even starker when you consider that without it, America would have had 3.6 million more babies born to teen mothers between 1991 and 2011. As of 2010, the state birth rates varied from a low of 15.7 in New Hampshire to 55.0 in Mississippi.

In addition to a two decade-long decline in the number of overall births, there has also been a five-year decline in the percent of preterm and low birth weight-babies born to teens. These poor pregnancy outcomes and their long-term effects on children are a major concern associated with teen pregnancy, so it is especially encouraging to see progress in that area.

Locally, New York City has one of the highest teen pregnancy rates in the country, but according to the city health department, it also experienced one of the sharpest drops in recent years, falling 27 percent over the last decade. Although the CDC did not offer any analysis of the factors leading to the drop in its latest report, New York City Health Commissioner Tom Farley was happy to share his thoughts on the city’s success. Farley believes that the city’s drop was a result of lower teen sex rates and greater birth control use. New York City public high schools make condoms available to students for free, and the city created an uproar in September 2012 when 40 school clinics started offering the morning-after-pill to students without parental consent. (Parents can opt out of allowing their children access to the pill, but only 1-2 percent of parents took advantage of this option.) As Farley puts it, teaching students about their birth control options doesn’t “increase their likelihood of being sexually active.” Instead, he said, “they get the message that sex is risky.”

While this recent data is certainly encouraging, the conclusions we can draw from it remain murky. Condoms were introduced to New York City’s public high schools in 1991, yet the sharpest decline took place over the last decade, and similar results were seen across the country. Meanwhile, despite progress in recent decades, the Bronx still has the highest teen pregnancy rate in the country. Overall, evidence supports the use of sex education programs that provide information on using and accessing birth control, while it wholly dismisses abstinence-only education programs. Across the nation, states with comprehensive sex education have far lower teen pregnancy rates than those with abstinence-only programs or no mandated programs at all. We seem to have figured out what fails without quite figuring out what works.

Perhaps the U.S. will be fortunate enough to continue experiencing a downward trend without fully understanding the factors causing it, but teen pregnancy is too important not to explore further. Among the bad news of the CDC’s finding is the fact that the U.S rate remains high when compared with other industrialized countries. The rates also continue to be different among different ethnic groups, with black and Hispanic girls still maintaining higher rates of teen pregnancy—and suffering the resultant health and education-related consequences that accompany it.

The national teen pregnancy rate is indeed lower, and we should take a minute to enjoy this rare piece of good news. Then, we should get back to work learning more about what works and determining how to make sure that all of our teenagers get the education and support they need to lower their pregnancy risk—regardless of their home state or skin color.