U.S. birth rates have been on a steady decline since 2007, but our procreation has reached a historic low: Birth rates are the lowest they've been since the government began tracking the data in 1909.

Theories on the declining birth rate range from the crappy economy to women choosing to being child-free, to the success of 16 and Pregnant and Teen Mom. Whatever the case, just 3.8 million babies were born in 2011—a drop of 10 percent from 2008. An all-time high of 4.3 million babies were born in 2007.

The U.S. fertility rate dropped again in 2012 and hit another record low—from 63.2 births per 1000 women to 63 births per 1000 women. In order to replenish the population of a generation, it takes 2.1 children per woman. U.S. birth rates have been below replacement level since 2007.