Business Issue #119 ·

230,000 Births: The Number the UN Got Wrong

Fertility's turning point in country after country lines up not with economic crises, but with the year smartphones arrived

Oswarld (Kwangseob Ahn) · GTM & AI strategist working the seam between technology and business

230,000 Births: The Number the UN Got Wrong

Opening

Dear reader, back in 2018 the UN Population Division made a prediction. “South Korea will record 350,000 births in 2023.” The actual figure was 230,000. A 50% overestimate. The institution considered the world’s best at population forecasting missed by that much—just five years out.

And this is not just a Korean story. Mexico, Brazil, Iran, Tunisia, Sri Lanka, and others—in 2023, fertility rates in all of these countries fell below that of the United States. A world arrived that the forecasting models never contemplated: developing countries having fewer children than developed ones.

Why did this happen? Housing prices? Childcare costs? Shifting values? All of those are real factors. But none of them explains the “suddenly” and the “everywhere at once.” To give you the conclusion up front: recent research points not at the economy, but at the smartphone. And the evidence is strikingly systematic.

🔍 Fewer Couples, Not Fewer Children

When people hear that fertility is falling, most picture the same scene: “Couples must be deciding to have just one child.” But when you pull the data apart, an entirely different picture emerges.

Stephen J. Shaw, a data scientist and demographer, decomposed birth data from the United States and other major developed countries and made a crucial discovery. The number of children per mother is stable—or even rising. What has fallen steeply over the past 15 years is the share of women who have even one child.1

Put simply: “It’s not that two-child couples cut back to one. Couples aren’t forming in the first place.”

The US data makes this even sharper. If America’s marriage and cohabitation rates had held steady over the past decade, the total fertility rate would actually be higher than it was ten years ago. The real driver of the fertility decline was the disappearance of couples.

And hiding inside this pattern is an uncomfortable K-shaped curve. Couple formation and childbearing among college graduates are stable or even increasing, while coupling and births are plunging among those with less education and lower incomes. Family formation itself is polarizing.

📱 The Year the Smartphone Arrived, Births Bent Downward

If economic explanations fall short, what can account for this “sudden” decline?

Nathan Hudson and Hernan Moscoso Boedo of the University of Cincinnati, in a paper published in April 2026, matched data on 4G mobile network rollout in the US and UK against fertility rates.2The result was unambiguous. Regions that adopted high-speed mobile connectivity earlier saw births fall earlier—and faster.

The methodology is worth pausing on. The team exploited differences in terrain ruggedness within the United States to generate natural variation in 4G coverage—mountainous areas get cell towers later. That makes the design close to a natural experiment. And by replicating the same pattern in data from England and Wales, they confirmed it cannot be explained by any single country’s contraception policies or welfare reforms.

But the truly chilling part is what appears when you scale this pattern up to the country level.

According to the Financial Times’ own data analysis, the inflection point of each country’s fertility decline overlaps with astonishing precision with the moment smartphones went mainstream in that country.

  • United States, United Kingdom, Australia: teen and twenties fertility relatively stable through the early 2000s, then a clear decline starting in 2007
  • France, Poland: the same pattern from around 2009
  • Mexico, Indonesia: around 2012
  • Iran, Egypt, Senegal: around 2013–2015 Overlay these dates with each country’s mass smartphone adoption (the point when Google searches for mobile apps surged), and a single unified trend appears. Whatever the prior trajectory—gentle decline, stability, even a slight rise—the pattern after smartphone adoption was identical: fertility plunged.

And the younger the age group, the steeper the drop. That is a precise mirror image of smartphone usage by age.

South Korea is the most extreme case of this pattern. In 2012 it became the first country in the world to pass 60% smartphone penetration, reaching 95% by 2018. Over the same period, the total fertility rate fell from 1.30 (2012) to 0.72 (2023). The country where smartphone adoption ran faster and deeper than anywhere else has the lowest fertility rate of anywhere on earth. The timing is far too precise to dismiss as coincidence.

🧩 “To Meet the One, You Have to Filter Through Many”

Why would smartphones depress fertility? The intuitive answer (“With easier access to contraception information, people just stop having kids—right?”) has already been rejected. Hudson and Moscoso Boedo’s core mechanism lies elsewhere.

Smartphones fundamentally restructured how teenagers and twentysomethings spend their time.

Time-use diary data from American adolescents shows in-person social time cut in half while digital leisure tripled. Korea is more extreme still: face-to-face social time among twentysomethings has halved in twenty years.

Demographer Lyman Stone explains the mechanism this way: “To meet someone you’ll marry, you have to filter through a lot of people. If social time falls sharply, matches become hard to find—or you never find one at all.”

He adds one more pointed observation: “When you spend a lot of time with peers in the real world, your expectations of a partner get grounded in reality. When you spend time on Instagram, your expectations get grounded in an artificial sense of what’s ‘normal.’”

This is not a simple “smartphone addiction” story. The social coordinate system itself has shifted. Once enough of your peers are on the smartphone, the smartphone becomes where the peer network lives. In-person time can only shrink structurally, and the “chance encounters” that used to happen inside that in-person time vanish.

Hudson and Moscoso Boedo formalized this as a coordination failure model. Once smartphone prices fall far enough, the in-person equilibrium can no longer sustain itself, and the entire economy shifts to a “phone-mediated equilibrium.” And this transition is observed simultaneously—via the same instrumental variable—in both the fertility collapse and the surge in teen suicide rates.

📺 The Precedent TV Already Set

In fact, the finding that media technology affects fertility did not originate in the smartphone era.

In 2001, Robert Hornik and Emile McAnany published research showing that the correlation between TV ownership and fertility decline was stronger than the correlation with income or education.

Then there is the famous 2012 study by Eliana La Ferrara of Bocconi University and her colleagues. They matched the region-by-region rollout of telenovelas (serial dramas)3 produced by the Brazilian broadcaster Rede Globo against fertility rates. These dramas depicted families with far fewer children than real Brazilian households—and in regions that gained access to Globo’s signal, fertility fell significantly. The effect was largest among women of lower socioeconomic status.

If TV had that much impact, the researchers reason, the smartphone—a medium that is used far longer and is far more personal—could have a much larger one. And the data backing that inference is now accumulating at the country level.

Alice Evans of Stanford University has given the phenomenon a name: “cultural leapfrogging.”4 “Instagram and TikTok let young women worldwide bypass traditional authority—by raising their expectations of relationships. The men are often not ready for that shift.”

The data actually bears this out. The more traditional a culture’s gender roles, the larger the smartphone’s effect on fertility. That context is also why the steepest fertility declines of the past decade have been observed in the Middle East and Latin America.

Oswarld’s Take

Reading these studies, I kept thinking of a pattern I have seen countless times while building GTM strategies.

When a technology product’s market penetration crosses a threshold (usually 40–60%), user behavior flips from “choice” to “default.” After KakaoTalk crossed half of Korea’s messenger market, being “the person who doesn’t use KakaoTalk” became socially awkward. Smartphones follow the same pattern. Korea passed 60% smartphone penetration in 2012—first in the world. From that point on, Korea’s fertility decline hit the accelerator on its way to the bottom of the OECD.

What these papers argue is not the simple causal claim that smartphones “directly” lowered fertility. It is that once technology adoption crosses a threshold, the basic structure of social interaction changes—and that structural change knocks out couple formation, the precondition for births.

People want to find the one “cause” of falling fertility. Housing prices, childcare costs, changing values. But the real danger is that these factors are not independent of each other. Social media amplifies economic anxiety and makes decades-long changes feel like a sudden wave. The smartphone is less a cause than an amplifier that accelerates multiple factors at once.

Which is why we must not slide into the linear fix of “regulate smartphones and fertility will recover.” Lyman Stone puts it precisely: “You don’t tell someone with bad eyesight to fix their genes. You give them glasses.” The technology cannot be rolled back. The real task is to design, on top of the social structure the technology has already rebuilt, the conditions under which people can meet again.

Closing

One. The core of the global fertility decline is not “couples having fewer children” but “couples not forming at all.” Births per mother are stable.

Two. Each country’s fertility inflection point coincides systematically not with economic crises or policy changes, but with the moment smartphones went mainstream there. The US in 2007, Mexico in 2012, Senegal in 2013–2015.

Three. The smartphone is less the “cause” itself than the trigger and amplifier of a pathway: less in-person social time → fewer chances to form couples → falling fertility.

The next time you pull out your smartphone, consider just one thing. Whether the 30 minutes you spent inside this screen might have been 30 minutes you could have spent meeting someone’s eyes in the real world.

References & Further Reading

Primary sources

Background

The author, Kwangseob Ahn, is a professor of business administration at Sejong University and lead consultant at OBF (Oswarld Boutique Consulting Firm). He teaches statistics and data analysis—including business data management and business analytics—at the university, while in the field he leads GTM strategy and AI strategy consulting, designing the interface between technology and business. He has published academic research on memory architecture for AI dialogue systems (HEMA) and runs Daily Arxiv, a project curating global AI papers every day. He completed a master’s program at Korea University’s Graduate School of Management of Technology and earned a KMBA there. He is the author of Homo Brainless: The People Who Outsource Their Thinking.

Footnotes

  1. Total Fertility Rate (TFR): the average number of children a woman is expected to bear over her reproductive years (ages 15–49). The “replacement rate” needed to maintain a population is 2.1. ↩

  2. Instrumental Variable: a method used to estimate causal relationships in research. Since “smartphone → fertility” is hard to measure directly, researchers infer causality through a mediating variable—terrain ruggedness—that affects only smartphone adoption and has no direct effect on fertility. It is a key tool for identifying causation in the real world, outside the laboratory. ↩

  3. Telenovela: a Latin American TV serial drama. Similar in format to Korea’s daily dramas, but typically structured to conclude in 100–200 episodes. In Brazil they draw nationwide audiences and carry enormous social influence. ↩

  4. Cultural Leapfrogging: a term used by Alice Evans of Stanford University. It refers to the phenomenon of young women, via social media, skipping over their own country’s traditional cultural stages and directly absorbing values and expectations set by global standards. ↩