While birth rates in the US have fallen to record lows, statistics show a marked and growing difference between the fertility of religious and non-religious families.

The Institute for Family Studies reports that the fertility rate among American women who identify themselves as religious has never fallen below 2.0, and remains above the “replacement level” (2.1) at which population would be stable. Among women who describe themselves as unreligious, however, the fertility rate is below 1.5, and has been declining steadily for a decade.