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New data from the CDC shows that teen birth rates are lower than they’ve been since the 1940s—and fell across all ethnic groups between 2007 and 2010.

In D.C., the teen birth rate fell 10 percent, from 50.4 births per 1000 teenagers to 45.4 births; the CDC deems it a “significant” change. The rate plunged even further in Maryland and Virginia—by 21 percent and 20 percent, respectively.

So why did this happen? The CDC is unwilling to say for sure, but tries to give some credit to contraception:

The impact of strong pregnancy prevention messages directed to teenagers has been credited with the birth rate declines (9–11). Recently released data from the National Survey of Family Growth, conducted by the Centers for Disease Control and Prevention’s (CDC) National Center for Health Statistics (NCHS), have shown increased use of contraception at first initiation of sex and use of dual methods of contraception (that is, condoms and hormonal methods) among sexually active female and male teenagers. These trends may have contributed to the recent birth rate declines (12).

Image via CDC