Behind a 1.13 Fertility Rate: Why Births Keep Falling Even as Marriages Hold Steady

Japan's birth count in 2024 was 686,061, falling below 700,000 for the first time in recorded history. That represents a year-on-year decrease of 41,227 (down 5.7%), with the total fertility rate at 1.15, the ninth consecutive record low.

What demands attention is that the number of marriages in the same year was 485,063 (up 10,322, or +2.2%). Marriages were rising, yet births fell sharply. This "divergence" signals a new phase in Japan's declining birthrate.

The Japan Research Institute (JRI), led by chief researcher Takumi Fujinami, projects the 2025 birth count at approximately 665,000 and the total fertility rate at around 1.13. Although the pace of decline has slowed from 5% annually (2022-2024) to about 3%, Fujinami notes that "young people's desire to have children remains low, and the number of married couples choosing not to have children is increasing."

The conventional narrative has held that "roughly 80% of the fertility decline is attributable to rising rates of non-marriage" (analysis by Miho Iwasawa, director at the National Institute of Population and Social Security Research (IPSS)). The lifetime unmarried rate has reached 28.25% for men and 17.81% for women by age 50, and non-marriage remains the dominant factor. However, since 2015, another mechanism has become apparent: the fertility rate among married couples themselves has begun to decline.

The Turning Point in Married Fertility

Until 2015, the married fertility rate (the birth rate among married women) had been trending upward. Married couples were increasingly likely to have children, functioning as a "push-up factor" counteracting the overall fertility decline.

This structure reversed around 2015-2016. Analysis by the Nikkei Shimbun points out that "the main reason the pace of decline in births accelerated from 2016 onward was the declining proportion of married people having children." The married fertility rate shifted from a push-up factor to a push-down factor.

The data from the 16th National Fertility Survey (conducted 2021) substantiate this structural shift. The completed fertility rate for couples married 15-19 years was 1.90, an all-time low. Yet mothers who had at least one child averaged a completed fertility of 2.01. This paradoxical gap means that "couples who do have children are having two, but more couples are exiting before the first child."

The share of married couples without children stands at 9.9%, with one-child couples at 19.4%. The proportion of couples with infertility treatment experience has reached 22.7% (1 in 4.4 couples), revealing a significant "wanting but unable" population.

Late Childbearing and the Lengthening Marriage-to-Birth Interval

The structural acceleration of declining married fertility is driven by the ongoing trend of late marriage and late childbearing.

The average age of mothers at first birth in 2024 was 31.0, up 1.9 years from 29.1 in 2005 over roughly two decades. Second births average 33.1 and third births 34.2, meaning the probability of giving birth after 35 rises significantly with each additional child.

Moreover, the average interval from marriage to first birth has lengthened to approximately 2.8 years as of 2024. The lengthening has been particularly pronounced since 2020, compounded by the COVID-19 "blank three years" (2020-2022). Even when marriage numbers recover, there is an inherent time lag of several years before the effect materializes in birth counts. The increase in marriages observed in 2024 will be reflected in births no earlier than 2026-2027, and short-term statistical improvements should not be overinterpreted.

The "Second-Child Barrier" and Economic Pressure

The gap between ideal and actual family size is widening. Couples' average planned number of children remains at 2.01 (stable), but the actual final number of children for wives aged 45-49 has declined to 1.81 (down from 1.86 in the previous survey). The top reason cited for the gap between ideal and reality is "the cost of child-rearing and education is too high."

Research published by the National Center for Child Health and Development in October 2025 found that child-rearing costs from ages 0 to 18 (through high school) total approximately 21.72 million yen. Adding four years of university (national/public, living at home) brings the estimate to 32-36 million yen. With the highest annual cost of 2.31 million yen falling in the first year of high school, the weight of education expenses in suppressing second and subsequent births is evident.

Tokyo's total fertility rate fell to 0.99 in 2023, the first time any prefecture dropped below 1.0. High urban housing costs further inflate child-rearing expenses, entrenching a structure of "urban-type low fertility."

What the Gap with IPSS Projections Reveals

In its 2023 population projections, the IPSS projected a medium-variant birth count of 749,000 for 2025. The estimated reality of 665,000 represents a gap of more than 80,000, essentially reaching the low-variant projection of 658,000.

More alarming is the fact that the IPSS had placed the 660,000-level in 2041. As JRI's analysis shows, the decline is running approximately 16 years ahead of schedule. This aligns with the finding in our previous article ("The Core of Japan's Declining Birthrate Is Not Childcare Support"), which identified a 17-year acceleration based on preliminary figures; the gap has not narrowed even with confirmed data and updated projections.

The speed at which projection assumptions are collapsing has direct implications for pension, healthcare, and long-term care system design. Benefit levels and contribution rates are calibrated to future demographic composition, and when those foundations erode more than a decade ahead of schedule, the sustainability of the systems themselves must be reexamined.

The Collapse of the "Advanced-Nation Model"

From an international comparative perspective, a new shift is underway.

France, which has invested 2.9% of GDP in family policy, had long been the "model country" for maintaining fertility. But its 2023 fertility rate fell to 1.68 (the lowest since 1946), with an estimated 1.62 for 2025. Sweden, despite maintaining family policy spending at 3.4% of GDP, saw its fertility rate plunge to 1.43 in 2024.

South Korea fell to 0.72 in 2023 (the only OECD country below 1.0), then edged up to 0.75 in 2024 (the first increase in nine years), though it remains at the global floor.

This simultaneous international decline carries an important implication. The long-standing policy premise that "investing 3% of GDP in family policy will sustain the fertility rate" is beginning to falter across the advanced world. Japan's family policy stands at 1.6% of GDP, below even the OECD average (2.3%), but even raising it to France-level spending would no longer guarantee a fertility turnaround.

The 2026 Year of the Fire Horse and the Limits of Policy

The year 2026 coincides with the once-every-60-years Year of the Fire Horse (hinoeuma). In 1966, the previous occurrence, births dropped by 25.4% year-on-year (approximately 460,000 fewer births), a dramatic dip driven by the superstition that girls born in a hinoeuma year would be strong-willed and shorten their husbands' lives.

The SOMPO Institute projects that the Reiwa-era hinoeuma effect will be "extremely limited." In an age of late marriage and late childbearing, the time cost of postponing a birth by one year is far greater than it was 60 years ago. Furthermore, the spread of social media has made counter-superstition information readily accessible (76.2% of those considering pregnancy or childbirth say they "do not care about the superstition").

However, even if the hinoeuma effect is minimal, the combination of lingering COVID-era disruption and the accelerating decline trend means that concern over a breach of the 600,000 mark in 2026 is not unfounded.

On the policy front, the "Acceleration Plan" formulated as part of the National Strategy for Children's Future in December 2023 commits 3.6 trillion yen over three years (FY2024-2026), but skepticism about its effectiveness runs deep. Professor Shintaro Yamaguchi (University of Tokyo) notes that "cash transfers do raise the birth rate, but the effect is not particularly strong," and OECD analysis by Associate Professor Yu Shibata (Kyoto University) found that only "immigration and childcare expansion" have a statistically significant positive effect on fertility, while child allowances were not significant.

The Structural Prescription: Rebuilding an "Economic Foundation for Marriage"

The structures examined in this article call for a reframing of the focus of declining-birthrate countermeasures.

First, the decline in married fertility cannot be addressed simply by expanding nursery capacity. Behind the decision of married couples not to have children lies the economic rationality of 21.72 million yen in child-rearing costs. If the effect of cash transfers is limited, what is needed is a more fundamental economic policy: structurally reducing housing and education costs.

Second, the lengthening interval from marriage to birth implies a delay in policy effects. When it takes nearly three years for improvements in marriage numbers to translate into higher birth counts, shifting policies in pursuit of short-term results is counterproductive.

Third, the faltering of the French and Swedish models exposes the limits of facile cross-country benchmarking. Given Japan's unique social norm that "children are born within marriage" (with an out-of-wedlock birth ratio of 2.5% compared to approximately 60% in France), building an "economic foundation for marriage" stands at the core of a Japan-specific approach to the declining birthrate.

As Masahiro Yamada argues in 『日本の少子化対策はなぜ失敗したのか?』(Why Did Japan's Declining-Birthrate Countermeasures Fail?), Japan's culture of "risk avoidance and concern for appearances" has neutralized the European-style childcare-centric approach. Correcting the "generational budget asymmetry" analyzed in our previous article (113.6 trillion yen for the elderly vs. 10 trillion yen for children) while directing those resources toward stabilizing youth employment and reducing housing costs constitutes the structural prescription for confronting this new phase of declining married fertility.

Related Practical Guide

References

Reference Books

• 『日本の少子化対策はなぜ失敗したのか? : 結婚・出産が回避される本当の原因』 (Why Did Japan's Declining-Birthrate Countermeasures Fail? The Real Reasons Marriage and Childbirth Are Being Avoided) by Masahiro Yamada (Kobunsha Shinsho, 2020): A foundational work in family sociology that demonstrates how Japan's culture of "risk avoidance and concern for appearances" has neutralized childcare-centric policies modeled on Western approaches
• 『結婚滅亡 : 「オワ婚時代」のしあわせのカタチ』 (The Death of Marriage: What Happiness Looks Like in the Age of Marital Extinction) by Kazuhisa Arakawa (Asa Publishing, 2019): A data-driven argument that non-marriage and late marriage are the primary drivers of the declining birthrate, including the paradoxical finding that "the number of children per married couple has not changed"