Their biological clocks may be ticking, but fewer U.S. women are listening—at least fewer young women.
The country’s birthrate hit a record low in 2016 with 62 births per 1,000 women of childbearing age, but that top-line figure conceals a main driver of the decline:
The birthrate among teenagers fell 9% from the previous year to 20.3 births per 1,000 women, the lowest figure for that age group since at least 1940.
The only group having fewer children was women ages 40 to 44. But unlike teens, the older women gave birth at a higher rate than the year before, increasing by 4% to 11.4 births per 1,000 women.
The National Center for Health Statistics released the latest general fertility figures for women of childbearing age, defined as ages 15 to 44, in September.
Women ages 35 to 39 also pulled down the overall average with 52.7 births per 1,000 women, an increase of 2%. But the rates of birth for the three remaining age groups were all substantially higher than the average.
Women ages 20 to 24 had 73.8 births per 1,000 women, down 4% from the previous year. Women 25 to 29 had 102.1 births per 1,000 women, down 2%. And women 30 to 34 had 102.7 births per 1,000 women, an increase of 1%.
Economists and others pay attention to fertility because it reveals how many people will be competing for food, property and jobs in the future, as well as how many will be available to support programs such as Social Security and Medicare.
Too few births, in the absence of mitigating factors such as immigration, could compromise the economy, but it’s possible today’s younger women are merely delaying pregnancy rather than skipping it altogether.
“That’s the question people are asking,” said Mark Mather, who specializes in U.S. demographic trends for the Population Reference Bureau, a nonprofit demographic-research group. “Will they catch up or will their completed fertility levels be lower than those of previous generations?”
It isn’t unusual for births to decline following an economic downturn—at the start of the 2007-09 recession, the general fertility rate was 69.3 births per 1,000 women—but general fertility is only one measure.
“This is an important piece of information, but it’s not a full picture,” said Brady E. Hamilton, a statistician who co-wrote the NCHS report.
A measure favored by some demographers is the total fertility rate, a projection of how many children a woman will have in her lifetime.
“Most demographers would tell you the total fertility rate is the preferred rate in terms of really getting at women’s propensity to have children,” Dr. Mather said.
The two measures are related.
The general fertility rate is calculated by dividing the number of live births by the number of girls and women who are of childbearing age. (The result is multiplied by 1,000 to get the rate per 1,000 women.)
Total fertility calculates the same rate by age or age group and then sums up the results to estimate the average number of children each woman will have during her lifetime. (If five-year age groups are used, the sum of the rates is multiplied by five.)
“It’s kind of a hypothetical number, but demographers like it because it’s essentially a projection of what would happen if today’s fertility rates were held constant through this girl’s lifetime,” said Gretchen Livingston, a demographer at Pew Research Center who is an expert on fertility.
At its low point in 1976, the total fertility rate projected that women of childbearing age that year would have an average of 1.7 children. The rate is now 1.8.
Other measures have also increased.
Completed fertility, a retrospective measure that shows how many children women ages 40 to 44 actually had, hit a low point in 2006 with an average 1.86 births per woman. It’s now at about 2 births per woman, or nearly replacement level. And the raw number of births bottomed out in 1973, when there were 3.1 million. Last year, there were 3.9 million.
“The total number of births has generally increased or remained steady over time even though fertility rates have declined,” Dr. Mather said. “This is because the total number of women of reproductive age in the U.S. has increased as the population has grown.”
Taken together, the different measures provide a more complete picture of fertility in the U.S.
Corrections & Amplifications
The birthrate among teenagers in 2016 fell 9% from the previous year to 20.3 births per 1,000 women. An earlier version of this article incorrectly stated the 9% decline referred to the teen pregnancy rate. (Oct. 20, 2017)