The Washington Post today ran a story ("U.S. Fertility Rate Hits 35-year High, Stabilizing Population") that follows up on an earlier report on 2006 birth rates from the Centers for Disease Control and Prevention (See our December 10 posting).  The Post story needs some clarification.

The earlier CDC report indicated that America's total fertility rate (TFR) rose to 2,101 births per 1,000 women in 2006-the highest such rate since 1971 and he first time since 1971 that the rate was above "replacement."  [TFR is the average number of children that would be born to a woman during her lifetime, while the "replacement level," generally regarded at 2.1 for industrial nations, is the level of fertility at which women, on the average, have enough daughters to replace themselves.]

While helpful and instructive in many ways, the Washington Post story and its headline could easily lead the reader to believe that U.S. population is stabilizing--neither increasing nor decreasing in size.  In truth, the U.S. population is still growing rapidly. Last year, U.S. population passed the 300 million mark and current projections show U.S. population rising to about 420 million by mid-century. 

That's because fertility rates alone do not determine the rate of population growth.  Population change has three factors:  births, deaths, and migration.  If death rates are declining and/or in-migration is exceeding out-migration, a nation's population can continue to grow even if the FTR is below "replacement rate."  In the case of the United States, death rates are continuing to fall, but more importantly, immigration is a major contributor to U.S. population growth.

The Post article not only confuses "replacement rate fertility" with "population stabilization," it suggests that "replacement rate fertility" poses no strain on the environment or natural resources:

While the rising fertility rate was unwelcome news to some environmentalists, the "replacement rate" is generally considered desirable by demographers and sociologists because it means a country is producing enough young people to replace and support aging workers without population growth being so high it taxes national resources.

That paragraph is misleading.  Every American consumes resources and leaves an environmental footprint.  In fact, we Americans have very large "footprints." While the U.S. population is only about five percent of the world's population, Americans account for about one-quarter of the world's annual consumption of fossil fuels and other natural resources.  When we read press accounts about the rising level of pollution and carbon emissions spewing out of China's industrial plants, we need to remember that those plants are making products for the U.S. and its expanding population.