The American baby boom and what it reveals about fertility
Analyzing the American baby boom from the point of view of opportunity cost
In a previous post on the effects of mandated curfews on fertility rates, I wrote:
I've illustrated this point with examples from Latin American countries, but similar situations are evident in other continents, where countries have experienced an increase in fertility rates under curfew conditions.
I now wish to discuss examples from continents beyond Latin America, where curfew conditions, or more properly wartime conditions, also led to an increase in fertility.
The Baby Boom and its causes
If you live in the Anglosphere (I don’t), or in any country at least moderately influenced by American culture, then you’ve probably heard about the American baby boom:
A baby boom is a period marked by a significant increase of births… The term "baby boom" is often used to refer specifically to the post–World War II (1946–1964) baby boom in the United States and Europe.
That period of time, 1946 to 1964 according to Wikipedia, was characterized by an exceptionally high birth rate compared to the preceding and subsequent years.
And, according to that same Wikipedia article, the cause of the baby boom was: “a strong postwar economy, in which Americans felt confident they would be able to support a larger number of children“.
Grok agrees on economic prosperity and optimism following World War II as a major cause, while also adding a second cause:
Delayed Family Formation: During the Great Depression and World War II, many couples postponed marriage and childbirth due to economic hardships and wartime uncertainties. With the return of economic stability and peace, these couples, along with younger adults who had delayed starting their families due to the war, contributed to a surge in birth rates. The pent-up demand for family life was released as conditions improved.
And a third cause:
Suburbanization and Housing Boom: The expansion of suburban areas facilitated by government policies like the GI Bill, which offered loans for home construction, made homeownership more accessible for many Americans. The move to suburbs often came with the cultural expectation of a larger family, which was reinforced by the design of suburban homes with extra bedrooms. This environment not only encouraged but also facilitated larger families, contributing to the baby boom.
All three causes imply that the American baby boom began following the end of World War II. However, if we stick to the significant increase of births definition, the baby boom actually began substantially before the war concluded:
In fact, as you can see in the previous chart, the American fertility rate experienced a notable increase from its 1930s low starting in 1940-1941 (I’ll address the 1944-1945 dip in just a moment).
While it is true that the peak of the baby boom occurred after WW2, there was nonetheless a large increase in fertility rates during the war itself. The global conflict was a time when restrictions on the availability of services and products were common in America, ultimately culminating in the enforcement of a curfew:
From the ritziest nightclub to the tiniest country saloon, all entertainment establishments across the country were ordered to dim their lights come midnight, causing the “biggest howl since prohibition.”
The official reason for the curfew was to conserve fuel and manpower for the boys overseas. But many reporters hinted that Washington also wanted to staunch the flow of money being tossed away “for fun” and redirect it towards war bonds.
Just as in the previous examples of curfews I’ve presented, the restrictions on leisure and socializing activities experienced by the United States during World War II seemingly made parenting a more attractive choice. In other words, as various other forms of entertainment and social interaction became less accessible or scarcer, having children became relatively more appealing.
On this point, I strongly recommend reading Alex Nowrasteh's article in Quillette, which delves into the relationship between opportunity cost and fertility rates:
…people who worry about low fertility focus on vague cultural explanations and don’t look at the simple one staring them in the face: microeconomics. Opportunity cost is what you must give up to buy what you want in terms of other goods or services, but the concept applies to every action you take. If I go to the movie theater on a Friday at 7pm, I give up the opportunity to spend that time watching a Netflix movie at home. The cost of going to the movie theater is watching the Netflix movie at home, or any other activity that’s second on my list of desires. The more options I have, the potentially higher the opportunity cost I face.1
The only way I can conceive for the first proposed cause of the baby boom - a strong economy boosting fertility - to be true, would be if this economic prosperity did not concurrently increase the supply of goods and services2.
Which is precisely the case of the United States economic boom during World War II. A large portion (most?) of the increase in economic output that happened during the war was captured by the American government to support the war effort.
The surge in production did not translate into significantly more services and products beyond what was available before the war. And I’ll presume that newborns were just as cute and adorable in 1945 as in 1939, thereby making the decision to have more of them quite appealing3.
The first proposed cause, a strong economy, only makes sense if it provides American prospective parents with more income while simultaneously restricting their options to spend it.
The second proposed cause, the reversal of war-induced delayed family formation, is not entirely accurate.
Let’s look at a chart depicting the mean age at birth (MAB) of American mothers during the war and post-war era. This metric represents the mean age of mothers at the time of giving birth and can be computed for all mothers in a given year regardless of whether it’s their first, second or subsequent child, or specifically for mothers having their nth child.
Notice that the MAB of first birth (red line) increases (older mothers) during the pre-war and war years, a trend typically associated with declining fertility rates. However, we already know that fertility actually increased during the war.
The answer to that riddle becomes apparent when looking at MAB for all births (blue line) which shows a decrease during the wartime years, with a small increase in 1944 and 1945. Women were increasingly delaying their first childbirth with each passing year (consistent with demographic transition theory, etc), but wartime conditions persuaded more women to have children and to reduce the gap between subsequent births.
And the most parsimonious explanation for the increase in MAB seen in 1944-1945, along with the slight fertility decline I noted earlier for those years, lies in the fact that the U.S. only deployed large number of men overseas for combat during the final years of the war. Despite what you might infer from sexting, having sex (and children) is rather difficult at a distance.4
Once those men were demobilized and female labor force participation decreased, the mean age at birth, particularly for first-time mothers, also declined. And fertility kept rising, reaching a total fertility rate (TFR) slightly above 3 children per woman during the late 1940s.
Just like women were susceptible to incentives when choosing whether to allocate their limited resources to parenting or its alternatives (when available), they were also susceptible to shifts in the labor market. And these shifts meant less career opportunities for women, making the prospect of motherhood more enticing.
There was actually no delayed family formation during most of the war5, with the exception of 1944 and 1945.
Baby booms and busts
The observation that post-war reduced female labor force participation influenced fertility rates implies that the baby boom cannot be entirely explained by the wartime conditions endured by the United States during WW2.
I interpret this to mean: wartime conditions, or curfew conditions, raise fertility rates from their prior levels, even though they are not the sole mechanism that can increase or lower fertility.
That being said, the impact of wartime conditions appears to consistently increase fertility, not only in the United States but across other nations involved in WW2.
Let's examine how (varying) wartime conditions influenced fertility rates in the major combatant countries participating in World War II:
You can see in the previous chart that wartime and post-war fertility trends in the United Kingdom mirror those in the United States: a moderate increase during the war, followed by a slight dip in 19456 when British soldiers were deployed to Europe, and a subsequent post-war increase. Japan7 also exhibits a similar pattern, with a less pronounced boom during the war years and a stronger decline in the final years of the war.
Germany and Russia8 on the other hand, showcase how wartime mobilization of large numbers of young men, along with combat occurring within national borders impact fertility: prospective mothers don’t want to birth a future orphan, leading to a sharp decline in the fertility rate.
Finally, France is perhaps the most interesting case among the countries included in this chart9.
At the onset of war, France saw a massive mobilization of its youth, with a corresponding decline in fertility. But following its defeat in 1941, France experienced a substantial raise in fertility, with TFR increasing from 1.9 to 2.3, during the German occupation10.
An occupied country is a bored country.
Just to make sure whether the increase in French fertility was related to the wartime conditions of an occupied country, let’s examine the fertility trends in other (wealthy) occupied countries during WW2.
Most occupied countries11 saw an increase in their TFR during the war, and also mirrored the subsequent post-war rise experienced by the major combatant nations12.
Notice that both the Czech Republic and the Netherlands experienced drops in fertility in 1945, likely due to their proximity to the frontlines of the ongoing war during late 1944 and early 1945.
Wartime without war
What about European countries that were not involved in the war?
Neutral nations, encircled by the theater of war, could not insulate themselves from the repercussions of the conflict raging all around them, and it seems only natural that wartime conditions impacted them in a similar way as combatants.
The following chart presents the fertility trends of Ireland, Sweden and Switzerland:13
As you probably expect by now, all three neutral countries experienced a rise in fertility during this global conflict, despite not fighting in the war.
The trend is clearer for the wealthier countries, Sweden and Switzerland, while less evident in Ireland, a country where per capita income was 40% to 50% lower than in Sweden and Switzerland14. My guess is that lower income resulted in fewer amenities, which might have provided alternatives to having children, even before the advent of war.
Also, notice that in these countries, in contrast with combatant and occupied countries, there was no post-war fertility peak in 1946 or 1947. Maybe due to the absence of returning soldiers eager to join the baby boom trend?
In conclusion, World War II fertility trends seem to imply that wartime conditions, provided they do not involve massive military mobilization, significant combat casualties, or famine, lead to increased fertility rates. Moreover, these conditions might have shifted culture towards a higher fertility lifestyle, even in countries not directly engaged in the fighting.
Of course, massive death and even famine were common in most wars before the 20th century, and in the few instances where these were absent, states were not strong enough to be able to extract nearly all “superfluous” economic production and direct it towards the war effort.
Yet the fact that these circumstances have become more frequent in the last century, along with their apparent effect on fertility, can tell us a great deal about current fertility trends.
“Misunderstanding the Fertility Crisis“, Alex Nowrasteh.
Or if it only very slightly increased their availability.
For a similar situation but without an ongoing war, think of a country experiencing an economic boom driven not by increased productivity or employment, but rather by a natural resources windfall.
The prospect of potentially bearing a child who might grow up without a father can be a deterrent for prospective mothers during times of war, but deaths of American soldiers (and civilians) were significantly fewer compared to other countries during WW2 - and other wars.
This also applies to marriages rates, which saw a spike immediately following the United States’ entry into WW2. See “Conscription, Family, and the Modern State_ A Comparative”, Dorit Geva, page 170.
Deployment was in 1944. Remember to always account for a nine-month lag when thinking about the causes behind of increases or decreases in fertility rates.
The 1966 dip is a well-known effect of a particularly Japanese superstition.
What looks like a baby boom during the years 1935-1937 is actually a recovery from the fertility decline caused by the Soviet famine of 1930-1933. And the drop in 1948 is probably the result of the 1946-1947 Soviet famine.
If you looked closely at the thumbnail of this post, you might have noticed that it doesn’t pertain to the American baby boom, but to the French one.
The increase was much steeper in the post-war period, as you can see in the chart.
I excluded poor occupied countries (e.g. Greece, Hungary) and those that were only partially occupied - where active combat took place - from the chart. You can’t get bored when you are trying to survive.
Though for Denmark it was only a modest increase from 2.98 in 1945 to 3.02 in 1946. Danish TFR went from 2.22 to 2.98 during the war (1940-1945).
I didn’t include Spain among the neutral European countries due to the lingering impacts of the Spanish Civil War (1936-1939) on its fertility rate. Also the fact that Spain was relatively poor at the time.