Brendan McDermid / Reuters

As the American population grows, so does the number of American moms. But, more than a century after Mother’s Day became an official holiday, even as that number increases, the share of the American population who are mothers is at the lowest point it’s been in a quarter century.

It’s frequently noted that fertility rates are falling sharply in richer countries, but the less observed consequence of this trend is that a decline in births can also mean a decline in motherhood in general. According to an analysis I ran of data from the Census Bureau, the decline of American motherhood is real, occurring very quickly, and may continue for some time yet.


The Share of Women in the U.S. Who Are Mothers

Ways to measure the share of mothers in the U.S. have changed over time. The top line shows the estimate of the number of mothers in the U.S., composited from the Census Bureau’s Current Population Survey. The bottom line is a census measure of women who report living with their own children in the home. (The Atlantic | Data: Current Population Survey, American Community Survey)

A few key points are legible in this graph. The first is that the time when moms made up the biggest part of the country’s demographics was from around 1975 to around 1995. (This is true for as far back as quality data is available—and possibly back to the nation’s founding, but mostly because of shorter life spans in earlier times, not lower fertility.) Since then, the share of the population composed of moms has eroded considerably. A holiday that once celebrated as much as 28 percent of the American population now celebrates less and less each year; a drop of a percentage point may not seem like much, but as a share of the country, it represents millions of people.

And there’s a natural follow-on trend to notice: As the dark gray line in the above graph shows, moms living with their own kids represent a shrinking share of the population too. This makes intuitive sense: Minors are much more likely to live with their parents than are the group of people with living mothers generally, and so if the fertility rate falls, so would the percentage of the population who are moms with kids in the house.

Not only are moms making up less of the population, but their characteristics are changing too, and in a way that might be linked to their proportional decline. Moms today tend to be older than in the past. Just looking at recent years, the change in age-specific birth rates has been drastic.


Number of Births Per 1,000 Women, by Age Group

(The Atlantic | Data: CDC)

In just the past few years, the peak childbearing age range for American women has advanced from 25-to-29 to 30-to-34. Meanwhile, childbearing among women under 20 has fallen by half or more, while childbearing among women 35 and older is rising.

One positive consequence of this age shift is that a larger proportion of new mothers are economically prepared to raise children. Less positively, however, many women find that, as they age, they can’t have as many kids as they would like. Plus, having children later in life can increase the risk of post-partum health complications. These finer points aside, one major consequence of the older-moms trend is that fewer years of a woman’s life are spent as a mother. This means that, at any given time, a larger share of women, and thus of the whole population, will report not having children in government surveys. In other words, later motherhood means less motherhood.

What is at the root of later-in-life births? Many people, especially many well educated people, are delaying marriage (for many reasons); even if people do eventually get married, they spend less of their life in a marriage, which tends to mean fewer babies. Furthermore, the wider use of contraception and developments in sex ed are contributing to much lower rates of teen pregnancy. It’s also possible that increased use of social media and pornography is leading to diminished frequency of unprotected, high-pregnancy-risk sex among teens: The idea is that with less face-to-face time, there’s a reduced supply of opportunities for spontaneous sex, and with more to do on phones, there’s also reduced demand for it.

On the higher end of the age distribution, the biological potential for childbearing is improving thanks to a panoply of fertility-enhancing medications, reproduction-assisting technology, better neonatal and OB/GYN care, and improved maternal education. As a result, women are having more kids later, although it is extremely unlikely that these later-in-life babies will offset the reduced earlier-in-life fertility.

Even as motherhood rates decline, Mother’s Day, of course, will endure. In fact, despite the demographic shift, retail spending on the holiday appears to be rising. (According to a trade group called the National Retail Federation, that’s happening rapidly, but since it’s a trade group, take that assessment with a grain of salt.) It is hard to say if Mother’s Day spending is rising more than one would expect given that the American population (and thus the absolute number, though not share, of American moms) keeps growing, but one factor might be that the proportion of women who are the mothers of adult children is rising. And those adult children may spend more generously when it comes to celebrating the moms they no longer live with.

Relying on an approximation of how many moms there are whose kids either live with them or don’t, it can be estimated how many empty-nester moms there are in the U.S., and how that’s changed over time.


The Share of Americans Who Are Empty-Nester Moms Is Rising

(The Atlantic | Data: American Community Survey)

Correlation doesn’t necessarily mean causation, but that rise since 2003 does align neatly with the National Retail Federation’s data showing when spending began to rise. What this may mean, ironically, is that as American motherhood declines, Mother's Day will only get stronger.

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