Waseda Firehorse Study: Women's Education Delays but Does Not Derail Family Formation in Japan

Waseda University Researchers Uncover Surprising Insights from Fire Horse Superstition

In a groundbreaking study published in the journal Demography on April 1, 2026, a team from Waseda University has leveraged a centuries-old Japanese superstition to provide causal evidence on one of the nation's most pressing demographic challenges. The research, led by Associate Professor Rong Fu from Waseda's Faculty of Commerce, examines whether women's higher education truly hinders family formation amid Japan's persistently low fertility rates. Using the rare 'Fire Horse' zodiac year of 1966 as a natural experiment, the findings reveal that education delays but does not diminish marriage or childbearing outcomes.

This work challenges long-held assumptions in East Asian demographics, where rising female university enrollment—now exceeding 50% of total students in Japan—has been blamed for delayed marriages and fewer children. With Japan's total fertility rate hitting a record low of 1.20 in 2024 and births plummeting to under 710,000 in 2025, the study arrives at a critical juncture, especially as another Fire Horse year looms in 2026.

The Origins and Power of the Hinoe-Uma Superstition

The 'Hinoe-Uma' or Fire Horse superstition stems from the 60-year Chinese zodiac cycle, where the combination of 'fire' and 'horse' is deemed inauspicious, particularly for girls. Folklore portrays Fire Horse women as strong-willed, independent, and prone to causing misfortune to their husbands, making them undesirable for marriage. This belief, rooted in Edo-period tales and reinforced by historical events like disasters in past Fire Horse years, peaked in 1966.

That year, births dropped by approximately 25%, from around 1.46 million in 1965 to just over 1.06 million. Prospective parents, fearing girl children, opted for selective abortions or contraception, skewing sex ratios and cohort sizes. The effect was stark: fewer girls entered schools starting in April 1967, creating smaller classes and reduced competition for limited spots in high schools and universities.

Historical precedents include minor dips in 1906, but 1966's scale was unprecedented due to post-war prosperity and access to family planning. As 2026 approaches, surveys indicate lingering awareness, though modern gender norms may blunt the impact.

Crafting a Quasi-Experiment: The Mismatch Cohort Innovation

Waseda researchers Rong Fu, Haruko Noguchi, along with collaborators Senhu Wang from National University of Singapore and Yichen Shen from Kanagawa University of Human Services, devised an ingenious quasi-experimental design. Japan's academic year begins in April, so babies born January to March 1967—post-Fire Horse—were grouped with the shrunken 1966 cohort for schooling. This 'mismatch cohort' enjoyed uncrowded classrooms and easier advancement to higher education without bearing the superstition's marriage stigma.

Comparing this group to peers born April-December 1967 (normal cohort), the study isolates education's causal effects. Using difference-in-differences analysis on vast datasets—the Japanese Census (1990-2015, ~1.8 million women), Vital Statistics on Marriage (1983-2018), and Vital Statistics on Birth (1992-2018)—they tracked outcomes from age 23 to 48.

This approach surpasses prior studies reliant on policy reforms or observational data, offering robust causality during an era of rigid gender norms (1960s-1980s).

Boosted Access to Higher Education: Quantifying the Gains

The mismatch cohort reaped tangible educational benefits. At age 23, university completion rates rose by 1.09 percentage points (7.8% relative increase), junior college by 0.90 points (1.9%). These gains persisted: by age 43, university rates held at +1.10 points, junior college at +1.72 points.

High school completion saw smaller, fading effects (+0.47 points at 23, +0.15 at 43), reflecting near-universal access already. Overall, the Fire Horse shock amplified women's postsecondary pathways, mirroring Japan's broader expansion where female university enrollment surged from under 10% in the 1960s to over 55% today.

Photo by Vitaly Gariev on Unsplash

Modest Delays in Marriage and Childbirth Timing

Higher education prompted subtle shifts in life milestones. Mismatch women married about 2 weeks later (0.04 years) and had their first child 40 days later (0.11 years). These delays equate to 0.1-0.4% relative to averages (marriage ~26.8 years, first birth ~29.6 years).

Spouses were marginally younger (-0.03 years), hinting at adjusted partner selection. No uptick in pre-marital cohabitation or non-traditional surname choices, underscoring enduring norms.

Long-Term Parity: No Fertility Penalty from Education

Crucially, delays proved temporary. At age 23, mismatch women were 0.49 points less likely to be married (-3.1%) and 1.03 points less likely to live with children (-5.3%). By age 43-48, gaps closed: marriage rates converged at 83-86%, fertility outcomes matched.

Education reshaped when, not whether, women formed families. This contrasts observational correlations linking degrees to childlessness, highlighting selection bias—ambitious women self-select into education regardless.

Empowerment at the Altar: Labor and Economic Shifts

More-educated women entered marriage economically empowered: 0.91 points higher labor participation, favoring small/medium (+0.54 points) and large firms (+0.27 points). Yet, they upheld traditions, suggesting adaptation within constraints.

In Japan, where women comprise 58% of university students (2025 MEXT data) but face 'M-curve' employment drops post-childbirth, this underscores structural hurdles over personal choice.

Japan's Women's Higher Education Boom Amid Fertility Slump

Japan's female university enrollment has skyrocketed: from 11% in 1975 to 56% in 2024, surpassing men. Elite institutions like Waseda boast near-parity or female majorities in humanities, social sciences. Yet fertility plunged from 2.0 in 1970 to 1.20 in 2024, births at 705,809 in 2025.

Policies like childcare subsidies yield limited gains; the study posits work-family incompatibility as culprit. Waseda's research reframes debate: universities empower women without derailing demographics.

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Policy Ramifications: Beyond Education to Structural Reform

Rong Fu notes: "Education's direct effect is moderate; institutional factors demand attention." Recommendations include paternity leave enforcement, flexible work, affordable childcare—aligning with Japan's 'womenomics' but needing vigor.

As 2026 nears, potential Fire Horse avoidance could test evolved norms, per Fu.

Looking Ahead: Waseda's Role in Demographic Research

Waseda, a top private university with 50,000+ students, pioneers such interdisciplinary work via its Faculty of Commerce and Political Science and Economics. Collaborations like this bolster Japan's research prowess, ranked high globally.

Future studies may track 2026 cohorts, informing policies for aging societies. For universities, it affirms educating women as demographic asset, not liability. Read the full Waseda press release and Demography paper.