A rocky road lies ahead to a far smaller world population.

Summary: We’re on our way to a far better world, one with a much smaller population. The world’s population will increase during the next 4 decades, and then begin a long steep drop. East Asia leads the way with its collapsing levels of fertility (Japan’s population has already rolled over), and the rest of the world follows. The road will be rocky unless we prepare for it. Here’s an introduction to the issue. You’ll be reading much more about this in the future.

UN Fertility Graph

The collapse in fertility rates is another one of these unexpected phenomena shaping our world that have been described on this website. How unexpected? To understand these things we should always look first at East Asia, where fertility has collapsed the most (or perhaps, fertility has been the first to collapse). Look at Japan. Over a quarter-century every forecast proved too optimistic. It might have found a floor. Or this might be a false hope.

BoJ looks at Japan's falling fertility
Ageing, Finance and Regulations“, speech by Kiyohiko G. Nishimura, Governor of the BoJ, 14 Nov 2012.

Experts don’t well understand what has caused this crash in fertility — although they have confidence in their theories — and have only guesses about effective public policy responses. But they understand the seriousness of this trend. How much does a nation’s population shrink after a few generations at fertility of 1.3 (approx the current forecast for Japan)?


Collapse of population at fertility of 1.3
Very Low Fertility: Consequences, Causes and Policy Approaches”, Peter McDonald, The Japanese Journal of Population, March 2008.

The 2nd generation after the present one will be only 40% as large as today’s. The 4th generation is only 15% as large.  These are astonishing numbers. The worst large-scale pandemics killed 1/4 to 1/3 of the affected population. Only the most severe wars inflict such damage. Unless we take massive and effective action, this outcome is almost certain.

The rest of the developed world is following Japan’s demographic path, and the emerging nations are following still further behind. The social and economic effects are difficult to even imagine.

Benefits and damages from a population crash.

Forecasts usually focus on the economic effects. Fewer workers (and less tax revenue) and more elderly dependents probably means slower growth and fiscal deficits. And persistent inflation — or deflation, depending on the economist. Here’s a more insightful analysis: “Aging and Deflation from a Fiscal Perspective”, Mitsuru Katagiri, Hideki Konishi and Kozo Ueda, November 2014. Get used to deflation.

Our analysis reveals that the effects of aging depend on its causes. Aging is deflationary when caused by an increase in longevity but inflationary when caused by a decline in birth rate. Numerical simulation shows that aging over the past 40 years in Japan generated deflation of about 0.6 percentage points annually.

While the economic effects will be large, they are foreseeable. The social changes are more difficult to understand. What will society look like when configured to support the elderly instead of children? When women’s careers are seldom sidetracked by children, and then only briefly? Our gender roles and institutions are configured for a world very different than that we can expect to see.

Snapshots of age distribution in an aging society
Very Low Fertility: Consequences, Causes and Policy Approaches”, Peter McDonald, The Japanese Journal of Population, March 2008.

History books are filled with struggles with low fertility, as far back as the empires of Hellenistic Greece and Rome. See Polybius’ warnings about demographic collapse from the 3rd century BC. Their struggles were usually in vain. Fertility declines are difficult to fix.

If we want to boost fertility, can we do so?

Fertility rates are difficult to change. The monumental social trends that produced this change — such as new contraceptives and feminism — are still in motion. Feminism is still evolving, each generation more radical than before. Another revolution in contraception lies ahead, a “male pill”, which will depress fertility still more, perhaps by a lot (we don’t know how much men want children).

But why should we see falling population as a problem? The next industrial revolution has begun, probably creating painful levels of unemployment. A falling working age population solves that problem, and the increased productivity of new tech provides a means to support the growing ranks of the elderly. Also, smaller populations reduce our burden on the environment. For more about this see Must our population always grow to ensure prosperity?

For More Information

Wikipedia has an excellent entry on sub-replacement rates of fertility. For details about the data and implications see the population website of the UN’s Department of Economic and Social Affairs, especially this summary article.

See the posts at the FM reference page about Demographics, with links to many useful articles. Also see the posts about the 3rd Industrial Revolution now under way. Some of special interest:

A look at past fear-mongering about overpopulation.

The Mark of Gideon“, Star Trek in 1969. We are excited repeatedly by these linear extrapolations of current trends, despite their long history of failure. The result is exaggerated and often false alarms, and public indifference to future warnings.



7 thoughts on “A rocky road lies ahead to a far smaller world population.”

  1. Another point I feel is important to mention because I’ve experienced it personally, is the relationship between urbanization and fertility rates.
    In an age where more of us live in the city, the high cost per square foot and per bedroom might cause young people might decide to have fewer children, and/or to delay parenthood until they’re able to afford more physical space in which to raise their children.
    We can see the extremes of this correlation in the most urbanized nations of the world; Japan and the “Asian Tiger” countries of Hong Kong, Singapore, Taiwan, and Korea, which not surprisingly also have some of the lowest fertility rates in the world.

    1. Your post reminded me of a book I read in my college days by Paul Ehrlich. Quite terrifying at the time.

      1. Harry,

        I hope not! Ehrlich preaches the certainty of cataclysmic doom unless we abandon capitalism and democracy. This post says we will have rising inequality and possible social disruption if we don’t manage the new industrial revolution. Perhaps episodic violence, as in our 19th C. But probably no cataclysm.

  2. You can’t stop population declines they are a result of dying civilizations; that dying process is a long term trend with many origin points; choices about when to have children, whom to have it with, how to meet that person in a very fast paced busy world, view of the life of that child good or bad. World leaders aren’t making the world a good place for people to feel comfortable bringing a child into the world, people have to have a basic faith in the future.

    That life in general will continue to improve, I for one don’t have such hope. Nothing in this world would give me confidence that a child born in the last fifteen years will have a better life than I. More likely there life is going to suck beyond the telling and each successive generations life will be even worse.

    1. Harry,

      I agree. But the population decline is a wonderful trend. With a lower population Earth can become a garden spot. Getting there will be difficult, as the population will rise due to its age distribution even as fertility falls. For details see: Must our population grow to ensure prosperity?

      As for the future, I disagree. There are challenges ahead — there are always challenges ahead — but to say “nothing in this world gives your confidence” shows a blinkered vision. Nothing? We have made great progress in the past several centuries, and I’d give us good odds of continued progress.

  3. It was the Emperor Augustus who first tried to address the decline in fertility among Romans, particularly Roman elites. The Empire did not achieve its heights until 200 years after Augustus and lasted for 250 years beyond that. Saying declining population means a dying society does not account for this important fact.

    I think people predicting the decline and fall of America are premature.

Leave a Reply

This site uses Akismet to reduce spam. Learn how your comment data is processed.

Scroll to Top
%d bloggers like this: