Controversy about Fertility Rates

Fertility data are in the news. There is even controversy. And, there is more to consider.

Back in October, several news services¹ ² ³ reported that the US hit a record low fertility rate of 63.2 with Rhode Island leading the way with a rate of 51.5. The Population Reference Bureau (PRB) commented in early December that this was technically incorrect as the General Fertility rate (GFR) [Total number of births to women aged 15 to 44 / Number of women aged 15 to 44) does not take into account differences in age structure among the female population.4

Using a measure that controls for age differences – the Total Fertility Rate – they reported that the lowest rates were reached back in 1976 – 1.76 vs 1.82 in 2011. Pew released a report at almost the same time that still used the record low GFR, but emphasized that the decline in this rate is primarily due to reduced fertility in the Hispanic population.

Who is right?

Both organizations are correct and provide useful commentary. The composition of US births has changed tremendously since the 1970s, when data that identified Hispanics was not formally collected. Population groups often have different marriage and family formation behavior. Thus it is worthwhile to disentangle fertility rates to see if the story line is true for all groups. In fact, Pew decomposes the Hispanic population as the foreign born and native born have reacted differently to the economic downturn.

For example, in 2011 Hispanics account for 23 percent of US births, whereas in 1991 the percentage was only 15. Comparing a rate in the 1970s with a rate in 2011 without accounting for compositional changes can be risky. One reason the TFR in might be lower in 1976 than it is in 2011 is that the race/Hispanic composition of US fertility has changed. However, the rate for White women in 1976 was 1.65, while it was 1.77 for non-Hispanic white women in 2011. So, 1976 was a true low point for white women, but not so for blacks who have only reached below replacement fertility in the last two years.

Below is a table that provides a broad view of changes composition of births and selected fertility rates over the past 20 years.

But, the total fertility rate is not a perfect measure either. It is a period measure – measuring the hypothetical number of births that a woman in 2011 would have if she followed the fertility behavior of all women in 2011. It can be volatile as the chart of TFR over time shows.

Figure 1: Total Fertility Rate (TFR): 1911 – 2010
Figure1
This measure does not necessarily reflect the total number of children a woman will have. For instance, the TFR in 1960 was over 3.65 and yet no cohort of women has ended up with that many children.

The following table shows the birth cohorts with the highest and lowest completed fertility.

Of course, the problem with cohort rates is that one has to wait for women to reach age 50. Most policy analysts are interested in the here and now or a best guesstimate of the future. So, policy analysts want to know which current measure best predicts future completed fertility – both the booms and the busts.

That measure is up for discussion, but there is a reasonable likelihood that some of the current birth cohorts will end up with fewer children than the women who contributed to that record low TFR in 1976. Likely contributions come from increasing ages at first birth, and an increasing proportion of childless by choice women.

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[1]Dougherty, Conor. 2012. “US Fertility Rate Hits Lowest Level on Record./a>” Wall Street Journal (October 3, 2012)
[2] Stobbe, Mike. “
Recession contraception? Birth rate down in US for 4th year.” Associated Press (October 3, 2012)
[3]Hamilton, Brady E. , Joyce A. Martin, and Stephanie Ventura. 2012. “Births: Preliminary Data for 2011.”National Vital Statistics Reports Volume 61, Number 5
[4]Haub, Carl. “Reports that the U.S. Birth Rate in 2011 was the Lowest in History Are, Well Wrong.” Behind the Numbers, PRB Blog on Population, Health and the Environment. (November 28, 2012)
[5]Livingston, Gretchen and D’Vera Cohn. “U.S. Birth Rate Falls to a Record Low; Decline is Greatest Among Immigrants” Pew Social & Demographic Trends (November 29, 2012)
[6]Martin, Joyce, et.al. 2012. “Table 1: Births: Final Data for 2010.” National Vital Statistics Reports, Volume 61, Number 1 (August 28,2012)
[7]Hamilton, Brady, Joyce Martin, and Stephanie Ventura. 2012. “Table 1: Births, Preliminary Data for 2011.” National Vital Statistics Report, Volume 61, Number 5 (October 3, 2012)
[8]Table 2. Cumulative birth rates, by live-birth order, exact age, and race of women in each cohort from 1911 through 1991: United States, 1961-2006

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