U.S. Birth Rates and Population Growth


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U.S. fertility

The United States, at a population of over 291 million, is the world's third most populous country, after China and India, and has the highest population growth rate of all industrialized countries.4, 12 Fertility, or births per woman, contributes to our population growth and must be addressed in order to achieve population stabilization.

Each year there are approximately 4 million births in the U.S. and 2.4 million deaths.24, 25 The growth due to natural increase (total births minus deaths) is therefore 1.6 million per year. Yet according to the Census Bureau's decennial census, U.S. population is growing by approximately 3.3 million per year.26

U.S. fertility first dropped to less than replacement level fertility in 1972,11 and by 2002 had dropped to a record low.19 (Replacement level fertility is 2.1 children per woman because of infant mortality - see terms). During most of the 1970s and 1980s women gave birth to fewer than 2 children on average, a rate insufficient to replace the population.11, 12 Because of population momentum, U.S. population would have increased to 255 million by 2020 and then gradually declined.11

In 2000, births increased 3% over births in 1999 - the third straight increase following nearly a decade of decline from 1990 through 1997.12 Now, the average number of children born to women over a lifetime is at 2.03 - slightly below replacement level.12

Fertility compared to other countries

U.S. fertility is dramatically higher than almost all other developed countries. Europe's aggregate fertility varies between approximately 1.3 and 1.5, depending upon region, and Japan is at 1.3.4

In less developed countries, fertility is the predominant factor driving population growth. For example, the fertility of Mexico is 2.84 and the U.N. Population Division projects Mexico's population to grow from its current 100 million to 140 million within the next 50 years, a 40% increase.13 (The Census Bureau actually projects a higher 153 million in 2050, a 50 percent increase27). China's fertility is 1.7, and is projected to increase to 1.85 over the next 50 years. Bangladesh is at 3.6, India at 3.1, Pakistan at 4.8, and Zambia at 5.9.4

The fertility of most developing countries is decreasing, but because of population momentum, their populations will continue to increase throughout most of this century. It is therefore especially important to offer significant family planning assistance now to high-fertility countries.

Unwanted births

Unwanted births accounted for approximately 400,000 U.S. births per year in the mid-1990's. This is a small fraction of U.S. yearly population growth - approximately 12% of our annual 3.3 million per year annual growth.26 Between 1990 and 1994 (inclusive) there were 19,573,000 U.S. births, for an average of 4,000,000 births per year. Of these, 30% or approximately 1.2 million per year were unintended.15

Of these unintended pregnancies, 2/3 were mistimed and 1/3 were unwanted.20 Thus, only about 400,000 births per year were unwanted. (Presumably most of the mistimed births would have occurred anyway, although delayed somewhat.) Naturally, all unwanted births should be prevented and progress is being made in this area.

The teenage birth rate dropped 28% between 1990 and 2002 according to National Center for Health Statistics preliminary data. The birth rate for teenagers declined in 2002 to 42.9 births per 1,000 women aged 15-19 years, 5% lower than in 2001 (45.3) and 10% below the 2000 rate (47.7). Birth rates for teenagers 15-17 and 18-19 years continued their steady decline. However, teenage birth rates traditionally differ considerably by race and Hispanic origin.20

Population momentum

Population momentum is the tendency for population growth to continue even after replacement-level fertility (2.1 children per woman) has been achieved. It is caused by a relatively high concentration of people in their childbearing years - by a population that is age-biased toward youth.

population momentum graph It takes a period of time equal to the average life expectancy (approximately three generations or 73 years in the U.S.) for a reduction in fertility to be manifested as a change in actual population numbers.28

As mentioned above, U.S. fertility first dropped to slightly below replacement level fertility in 1972. Because of population momentum, however, U.S. population would have continued to increase to 255 million by 2020 - without any additional immigration - and then would have gradually declined.11, 17, 18

It is therefore crucial that this time delay be considered when targeting future population numbers and that steps to reduce fertility are taken sooner rather than later. Any attempt to achieve U.S. population stabilization must consider the long-term impact of both birth rates as well as immigration.

Causes of U.S. population growth


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        Author: Fred Elbel. Edited by Dick Schneider.


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