Birth rates affect the potential size of the workforce, GDP, debt, and other macroeconomic indicators. Demographers and economists measure fertility using several different measures. Each measure has its advantages depending on the research focus. This post reports fertility trends from 2006 through 2019 for several of the most prominent measures. Data comes from the American Community Survey (ACS).
The Age-Specific Fertility Rate (ASFR) measures the annual number of births to women in a specific age cohort (typically a five-year age cohort, e.g., 24 to 29) per 1,000 women in that cohort. This measure relates the actual number of births to an age cohort within a year. The ASFR is useful for analyzing life-cycle patterns of fertility but cannot be used to track changes in the total fertility rate because the underlying population’s age distribution changes over time.
Please view online for additonal years.
Figure 1 plots the ASFR of women ages 15 to 49 in five-year age cohorts over the years 2006 through 2019. Teenage pregnancies decreased from a peak of 28 births per 1,000 women ages 15 to 19 in 2007 to under 11 births per 1,000 women in 2019. Fertility peaked in the 25 to 29 age group from 2006 through 2011 but peak fertility has risen to the 30 to 34 age group. Over this period, the number of births also increased for the three oldest cohorts: for example, the average number of births per 1,000 women ages 40-44 rose 40 percent from 15 to 21 births per 1,000 women. This indicates women have been delaying fertility and having children at older ages than has historically been the case.
The Total Fertility Rate (TFR) is the number of children a woman would have if she instantaneously progressed through all childbearing years with the given ASFR at each age.1 The TFR is a theoretical measure of fertility that provides an idea of what fertility looks like on a yearly basis. Calculating the TFR requires only a single year of data and provides a reasonable comparison of fertility across years. However, the TFR does not reflect completed fertility over a woman’s lifetime and can be skewed by timing changes in fertility. For example, if women in a certain age cohort postpone fertility, that delay will show up as a drop in TFR when that cohort is early in their childbearing years ceteris paribus.
The TFR is typically the measure used in discussion of a population’s replacement rate, the rate required to maintain a population’s current size, disregarding any potential migration effects. The concept of the replacement rate has been in place since around 1930 and is equal to about 2.1 for the U.S. (as for most developed countries). A number above 2.1 is associated with a growing population, and anything lower than 2.1 indicates population decline.
Figure 2 plots the calculated Total Fertility Rate (TFR) from 2006 through 2019. The TFR rose between 2007 and 2008 to approximately 2.2 births per woman, but fell below the replacement level in 2010, and continued declining further to 1.7 in 2019.
The General Fertility Rate (GFR) is a ratio that measures the number of births per 1,000 women of childbearing age. Like the TFR, the GFR provides a good picture of current fertility or fertility within a given year. Unlike the TFR, the GFR is not age-specific and is a measure of actual births. The GFR has the advantage of being easy to explain, but it is driven largely by changes in the underlying age structure of the population. For example, women in their 40s have very few children. So, as the share of the female population over 40 increases, the GFR will decrease even if the ASFRs and TFR are not changing.
Figure 3 plots the calculated General Fertility Rate (GFR) in births per 1,000 women from 2006 through 2019. The GFR followed a similar pattern to the TFR, rising in 2008 when it reached 60 births per 1,000 women of childbearing age, then declining. In 2019, births had fallen off to 51 per 1,000 women of childbearing age.
The Completed Fertility Rate (CFR) measures the number of children women had over their lifetimes. This measure can only be calculated for cohorts of women who are beyond childbearing years. CFRs give the most accurate measure of lifetime fertility but are not useful in calculation of current fertility rates, which are determined by women still at childbearing ages. We do not calculate CFRs because recent ACS surveys do not ask women how many children they have ever had.
This analysis was conducted by Maddison Erbabian and Victoria Osorio. Prepared for the website by Mariko Paulson.
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“Childbearing years” is defined as ages 15 to 49, consistent with most of the literature. ↩
Year Age Group Births per 1,000 Women 2006 15-19 27 2006 20-24 94 2006 25-29 117 2006 30-34 103 2006 35-39 56 2006 40-44 15 2006 45-49 4 2007 15-19 28 2007 20-24 92 2007 25-29 118 2007 30-34 102 2007 35-39 55 2007 40-44 16 2007 45-49 4 2008 15-19 28 2008 20-24 96 2008 25-29 122 2008 30-34 107 2008 35-39 57 2008 40-44 18 2008 45-49 7 2009 15-19 28 2009 20-24 93 2009 25-29 113 2009 30-34 104 2009 35-39 59 2009 40-44 19 2009 45-49 6 2010 15-19 26 2010 20-24 85 2010 25-29 109 2010 30-34 102 2010 35-39 56 2010 40-44 18 2010 45-49 6 2011 15-19 23 2011 20-24 81 2011 25-29 106 2011 30-34 102 2011 35-39 56 2011 40-44 20 2011 45-49 7 2012 15-19 20 2012 20-24 77 2012 25-29 99 2012 30-34 100 2012 35-39 56 2012 40-44 17 2012 45-49 6 2013 15-19 19 2013 20-24 75 2013 25-29 102 2013 30-34 100 2013 35-39 57 2013 40-44 17 2013 45-49 5 2014 15-19 17 2014 20-24 73 2014 25-29 98 2014 30-34 103 2014 35-39 57 2014 40-44 17 2014 45-49 5 2015 15-19 16 2015 20-24 67 2015 25-29 98 2015 30-34 103 2015 35-39 58 2015 40-44 17 2015 45-49 5 2016 15-19 14 2016 20-24 67 2016 25-29 99 2016 30-34 105 2016 35-39 61 2016 40-44 19 2016 45-49 5 2017 15-19 12 2017 20-24 64 2017 25-29 95 2017 30-34 106 2017 35-39 62 2017 40-44 21 2017 45-49 7 2018 15-19 11 2018 20-24 59 2018 25-29 93 2018 30-34 104 2018 35-39 64 2018 40-44 21 2018 45-49 9 2019 15-19 11 2019 20-24 56 2019 25-29 89 2019 30-34 103 2019 35-39 62 2019 40-44 21 2019 45-49 8
Year,Total Fertility Rate (TFR) 2006,2.1 2007,2.1 2008,2.2 2009,2.1 2010,2 2011,2 2012,1.9 2013,1.9 2014,1.9 2015,1.8 2016,1.8 2017,1.8 2018,1.8 2019,1.7
Year,Births 2006,57 2007,57 2008,60 2009,59 2010,56 2011,56 2012,53 2013,53 2014,53 2015,53 2016,54 2017,53 2018,53 2019,51