Why did so many Japanese families avoid having children in 1966?

Last week, I was presenting at a conference and discussing the merits of animated visualizations vs. small multiples. On one of my slides, I presented the following chart that shows the total fertility rate (i.e., the average number of children born per woman) for the U.S.A. and Japan over a 60-year time period.


After the talk, one of the audience members came up to me and asked why there was that weird blip in Japan’s fertility rate in 1966. It turns out that there’s a fascinating explanation — an explanation that finds its roots in astrology and superstition.

Astrology and superstition

If you were born in the U.S. (or many other Western countries), you were probably assigned an astrological sign based on the day you were born: Aries if you were born between March 20 and April 19 (roughly), Taurus if you were born between April 19 and May 20, and so on. Each of these signs are associated with personality traits and various other features.

The Japanese use a similar astrological system, but one instead based on the Chinese zodiac. Along with assigning an astrological beast based on your birth year, each year also has one of the Five Elements associated with it—all that dramatically affect what your astrological sign entails.

Astrologers would like us to believe that our personality—and even our entire lives—are guided by these signs, but most people don’t take these predictions too seriously. In 1966, however, many Japanese families were still quite superstitious—and that’s why we see that blip in fertility rates in 1966.


You see, 1966 was the year of 丙午 (Hinoe-Uma), or the “Fire Horse.” As one source describes:

Girls born in [1966] became known as ‘Fire Horse Women’ and are reputed to be dangerous, headstrong and generally bad luck for any husband. In 1966, a baby’s sex couldn’t be reliably detected before birth; hence there was a large increase of induced abortions and a sharp decrease in the birth rate in 1966.

Instead of taking the risk of raising a “Fire Horse Woman,” whose headstrong nature would bring bad luck for her future husband, many Japanese families avoided having children entirely in 1966. In essence, superstition was embedded so deeply in Japanese culture that we could measure its effects on a macro-population scale.

Time will tell if superstition will strike again 10 years from now in 2026, the next year of the “Fire Horse” in its 60-year cycle. Given that Japanese is already below the replacement fertility rate (i.e., roughly an average of 2 children per woman), the result could be disastrous.

Dr. Randy Olson is the Chief Data Scientist at FOXO Bioscience, where he is bringing advanced data science and machine learning technology to the life insurance industry.

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16 comments on “Why did so many Japanese families avoid having children in 1966?
  1. Alan Christy says:

    This was the subject of a dissertation from Washington State University in 1978, written by my father-in-law, Takenori Aso. Here’s a link to the title in popline: http://www.popline.org/node/455133
    He also published an article in the spring issue of 1974 on the question in The International Review of Modern Sociology, addressing whether the drop was due to abortion or contraception.
    He was drawn to the subject, my wife says, because his daughter (again, my wife) was born in 1966. Sadly, he passed away suddenly last year, so we can’t go to him to talk about this some more.
    I doubt this is central to the work you do, but I thought I’d add a couple more sources to your list, in his memory.

    • Randy Olson says:

      Thank you for sharing, Alan! This is a fascinating topic and I can understand why your father-in-law was drawn to it. Always happy to have more academic sources posted here.

      • Alan Christy says:

        It was nice to see this come up. It gave my wife and me a chance to look again at her father’s work, a sweet moment seven months after his passing. Thank you!

    • Erik Fucito-Robinson says:

      Is she headstrong thou?

      • Alan Christy says:

        (Smiling): She is a beloved partner of 25 years who knows her own mind. More fire-horse women, please!

  2. erik_t says:

    A shrinking population isn’t disastrous. It’s less strain on resources. The Japanese aren’t going extinct.

  3. erik_t says:

    A shrinking population isn’t disastrous. It’s less strain on resources. The Japanese aren’t going extinct.

    • my eyes are hungry says:

      Except when other countries with too many people run out of resources and realize you still have them. Then they come flooding in and/or demand equality and ask why aren’t you sharing those resources.

      • snarkycomments says:

        Ahh… the Mutually Assured Destruction theory of demographics: it’s disastrous to not have lots of kids because if we don’t other people’s kids might move in and take our stuff.

        • Joshua Garcia says:

          well it is kinda true. Look at what is happening to california after white people left it post WWII. Of course white people took it from the mexicans originally but that only enforces number of people = bigger army diplomacy.

    • Peter.B.H. says:

      Disastrous mostly to the current makeup of economic system that is built on and direly relies on growth, and through that, demographic growth. You will note that economists in Europe are widely emphasising that population growth is only barely kept above replacement due to immigration and the higher fertility of immigrant women.

      • erik_t says:

        I’ve heard this, but it’s wrong-headed for several reasons. Automation is replacing a lot of jobs previously done by humans. This is growth through productivity. If these people don’t have jobs the government takes care of them.

        In the animal world when you have exponential population growth sooner or later you run out of resources and they are left with a lot of miserable dying animals. The economy is a human construct. There are pro-growth policies that can be implemented that don’t rely on population growth, e.g. restructuring the debt which would cause some temporary pain or with fiscal stimulus.

        • Peter.B.H. says:

          “The economy is a human construct.”

          No it is not. Look up the definition of it in any textbook. It is the systematic treatment of the facts of existiences in a world with limited resources, irrespective of current-day ideological bickering and the intrisic imprecision of any adolescent discpline.

          Also, economic growth is not the same as growth in material output, unless we are resorting to COMECON-style economic planning. From ubiquituous automated production to a government-managed Universal Basic Income is not an simple process, so no, it is not wrongheaded as such, as the solution you assume is not available at the snap of your fingers.

  4. @killbyte says:

    This is the exact kind of woman humanity & the world lacks!

  5. Jim Rose says:

    I am not surprised that there is from my time living in Japan.

    In addition to a fascination with blood group types and how people of the same blood group could work together better, the Japanese also were so fascinated by astrology that companies hired an astrologer is to advise them on their business plans.

  6. Sunil Singh says:

    check all news about the jobs of govt organistaion on govtjobsnews