...If abortion rates are falling because it has become harder or more costly to get an abortion, then a falling abortion rate is bad news for crime. As the “price” (whether in monetary terms, social stigma, having to travel a long distance, etc.) rises, women who otherwise would have sought an abortion will not get one. This suggests that more unwanted children are being born, and thus crime rates may rise in the future.

On the other hand, there are other reasons why the number of abortions might fall, and none of these have dire crime implications. For instance, because abortion has been legalized since the 1970s, there may be fewer women today who are seeking abortions — the women who might have been at highest risk for unwanted pregnancies today may never have been born.

A second scenario in which low abortion rates don’t lead to high crime is an increase in reliable birth control. For instance, following the increased spread of AIDS and other sexually transmitted diseases in the 1990s, condom use may have risen. More condoms would lead to fewer conceptions, including fewer unwanted conceptions. The result would be both a lower abortion rate and a lower number of unwanted births.

A third possibility is that the demographic most likely to obtain abortions is conceiving less for other reasons — including, possibly, less sex. My student Amee Kamdar has a fascinating paper in which she shows that incarceration of twenty-something males greatly reduces the number of teenage births. Indirectly, the continuing rise in incarceration may be contributing to reduced rates of both teen births and teen abortions.