The year was 1966. Japan, riding the high of its postwar economic boom, was transforming fast. Cities were shimmered with neon lights and bullet trains zipped past sprawling urban areas. Everything pointed to a bright, forward-looking future.

Or so it seemed. In 1955, suddenly and seemingly inexplicably, the birth rate plummeted.

Not just a little — but by nearly half a million births.

The fertility rate dropped from its usual 2.0–2.1 children per woman to 1.6. The birth rate fell by 26% in a single year. There was no war, no famine, no economic shock. Everything seemed to be going fine, it was as if an invisible hand had pressed pause on procreation.

That hand, it turns out, was superstition.

Hinoe-Uma: The Fire Horse Fear

The culprit was an ancient belief known as Hinoe-Uma, or Fire Horse. According to the traditional Chinese zodiac, which Japan adopted centuries ago, every 60 years brings a Fire Horse year — when the elemental sign of fire coincides with the animal sign of the horse.

The system combines two cycles: one of twelve animals (like horse, dragon, or tiger) and another of five elements (wood, fire, earth, metal, and water). Every year is assigned one animal and one element, and the full cycle repeats every 60 years. When the “fire” element aligns with the “horse” sign — forming the rare and feared Fire Horse year — it’s believed, especially in Japanese folklore, that girls born under this sign will be dangerously headstrong and bring misfortune to their families.

The last one before 1966 had been in 1906. And both times, Japanese birth rates dropped.

The superstition goes like this: girls born in a Fire Horse year are believed to be headstrong, ill-fated, and cursed to bring misfortune — especially to their husbands. “She will have great difficulty finding a husband,” wrote sociologist Koya Azumi in a 1968 article, “and the Japanese just weren’t taking that chance”​

In the age before prenatal sex determination, there was no way to know if a baby would be a girl. So, rather than risk it, couples chose not to have children at all.

Modern contraception was already widespread in Japan, and so was abortion. “During the last half of 1965 the number of induced abortions rose sharply,” Azumi noted. “People were still engaging in their usual sexual activities but, for some reason, they were determined not to have children.”

But it gets even weirder.

A Statistical Anomaly

That determination to follow superstition left a visible scar in the nation’s demographic records. Population pyramids show a striking indentation for those born in 1966. The United Nations data confirms that Japan’s birth rate dropped by over 20%, from 18.5 births per 1,000 people in 1965 to just 14.5 in 1966​.

It wasn’t just fewer babies, however. There were other distortions.

Victor Grech, a pediatrician and demographer, found that the sex ratio — the proportion of male births to total births — rose significantly in 1966. The number of boys born that year was unusually high. Why? Grech suggests that parents may have “deliberately misattributed the birth year for female babies” to 1965 or 1967. Essentially, people were trying to cheat the zodiac. He also notes that abortion likely also drove the reduction in total births.​

The pattern echoed what happened in 1906, the previous Fire Horse year. Then too, the number of male births jumped, while the number of girls appeared to decline. That time, it’s suspected many families simply falsified birth records to make it seem their daughters were born in safer years​.

What Will Happen in 2026?

The next Fire Horse year is 2026. Will the curse strike again?

By 1966, Japan was an advanced industrial society. Illiteracy was nearly gone. Urbanization had transformed the labor force. And yet, many families still acted as if a woman’s birth year could determine her fate. Even as arranged marriages dwindled — from 70% in the 1940s to just 5% by 2010 — cultural memory lingered.

Many modern Japanese families have largely shed many of these beliefs. Most marriages are now based on love rather than parental matchmaking. But superstition isn’t gone.

People can also find data to justify such beliefs.

That collective anticipation of discrimination created a self-fulfilling prophecy. Women born in 1966 have faced measurable disadvantages, including lower income levels and poorer educational outcomes compared to women born in nearby years​. This is more likely to be owed to discrimination than anything else but it is still a measurable impact.

We’re supposed to be living in the age of science and reason, but that was also the case in 1966.

The Fire Horse saga is a reminder that ancient beliefs can outlast logic — and that culture, not just knowledge, often shapes the choices we make about life, death, and the future.