The Centers for Disease Control and Prevention are reporting that U.S. total fertilty rates continue to fall. Total fertility is the number of children a cohort of women is expected to have over the courses of their lives. In general, the replacement fertility rate is considered 2.1 children per woman. In the new data, the agency traces fertility rates between rural, small metro, and large metro areas. Demographers have long known that increased urbanization tends to lower fertility and that is what the CDC finds in the data it reports. In 1970, 73.6 percent of Americans lived in urban areas; now 82 percent do.

The report notes that "since the most recent peak in the total fertility rate in 2007, the United States has experienced a decreasing total fertility rate and an increasing mean, or average, age of mothers at first birth."

In addition, the fertility rates for white, black, and Hispanic residents have all been falling since 2007. For example, in large metro areas the white fertility rate dropped from 1,820.5 to 1,575.5; the rate for blacks from 2,131.5 to 1,789.0; and for Hispanics from 2,754 to 1,929.5. Urban fertility rates for all three ethnic groups is now below replacement. The average age of first birth in metro areas is now 29 years old for white; 25.6 years old for blacks; and 25.4 years old for Hispanic residents. Keep in mind that the mean age at first birth was 21.4 years old in 1970.

Among other things, falling fertility rates are an indication that folks are less subject to the vagaries of nature and are now availing themselves of their increasing power to choose the number of children that they wish to have.