New Projection Speeds Up Global Population Decline. NewsWire

newswire: 8/3/2020

• A new study predicts that the world population will peak decades ahead of the UN forecast thanks to declining fertility rates. Instead of the year 2100, the study estimates the global population will peak in 2064 and that the elderly will also make up a larger share of the total than the U.N. projects. (The Lancet)
• NH: Forty or fifty years ago, most demographers subscribed to apocalyptic long-term forecasts of unsustainable global population growth. Paul R. Ehrlich, in his best-seller The Population Bomb (published in 1968), announced that it was already too late: Soaring birthrates would condemn humanity to massive famines and raw-material shortages. Hundreds of million would die of starvation in the 1970s, and there would be Malthusian food shortages even in the United States by the 1980s.
• In the decades since, demographers have been steadily pulling back on their long-term demographic growth scenarios. Why? Mostly because of steady and unexpected declines in fertility across most of the planet. It wasn't just that the postwar "baby boom" in the high-income world had clearly collapsed. It was also that birth rates were steadily falling in most low-income societies, from East Asia to Latin America. By around 2000, demographers were anticipating that the global total fertility rate (TFR) would eventually stabilize at some level under 2.1 (the replacement rate) and that the global population would eventually plateau or decline.
• In its last revision of its World Population Prospects in 2019, the UN Population Division (UNPD) forecasted for the first time in its "medium scenario" that the global population would peak (at 10.8 billion) by the year 2100--exactly in the year 2100, as it happened. (See "UN Projects the World Population Will Stop Growing by the End of the Century.") Just two years earlier, in 2017, the UNPD expected that it would hit 11.2 billion by 2100 and would still grow for some time thereafter.
• While the UNPD projections are widely regarded as setting the professional gold standard among demographers, they have also been the slowest to recalibrate their forecasts downward. The current US Census IDB forecast, for example, tracks slightly below the UNPD forecast in every year through 2050 (its limit). The highly respected International Institute for Applied System Analysis (IIASA) in Vienna has a much lower medium (or most likely) global forecast, which peaks at 9.4 billion in 2070 and thereafter declines. Indeed, a growing number of demographers now declare that accelerating population decline, not population growth, is the most dire long-term demographic challenge facing in the world. (See "How Prepared Are We for the Global Population Decline?")
• In general, the growing ranks of population declinists believe the UNPD pays no attention to--and therefore underestimates--the long-term social and cultural forces driving fertility lower across most of the world. These include greater affluence, growing urbanization, rising educational attainment (especially among women), increasing individualism and free-agency (i.e., markets), the socialization of retirement, and growing secularism--that is, declining religiosity. The UNPD demographers believe that societies manifest a long-tendency to gravitate back up toward a replacement rate TFR of something close to 2.1. Accordingly, they assume that today's very low fertility societies (e.g., in Europe and East Asia) will experience rising TFRs over the next several decades. The radical declinists reject this assumption. They see no reason to expect a TFR reversal in any society.
• The new Lancet study, authored by a large team headed by J.L. Murray at the University of Washington's IHME (yes, this is the same institute that I regularly cite in my COVID update), subscribes to this declinist perspective. According to the New York Times, it "challenges" the UNPD's forecast. Rather than assume that below-replacement TFRs will simply "gravitate back up," the Lancet team ties each society's TFR to two critical variables: Average years of educational attainment and availability of female contraception expressed as a ratio to the number of women who express a desire to limit their family size. This approach is similar to that of Wolfgang Lutz at IIASA. The authors find a very high correlation between these two variables on the one hand and completed female fertility by age 50 on the other. (In the chart below, CCF50 means "completed cohort fertility at age 50.")

• By assuming that education and contraception availability will trend upward with time and with per-capita GDP growth, the team's projections are tilted toward lower fertility and lower population growth almost everywhere. The authors introduce several other methodological innovations which, though much less consequential, are arguably superior to the UNPD's current practice. For example, they project future TFRs not on the basis of historical TFRs but on historical completed cohort fertility rates at age 50, which are much more stable than annual TFRs. This is smart. They also track per-capita GDP in every nation, which helps them estimate the rate of improvement in education as well as the economic drivers pushing migration from one nation to another. (The UNPD does not track any economic indicator.)
• The most likely projection according to this new model: Global population will peak in 2064 at 9.73 billion. This peak will occur 36 years earlier than the most recent UNDP projection--and at a number that is 11% lower. By 2100, the global population will decline to 8.79 billion and the global TFR will be 1.66--slightly beneath where the US is in 2019 (1.71). Also by 2100, 183 (of 195 nations) will have TFRs beneath 2.1 and 23 nations will have population declines of over 50% since 2017. These latter include Japan, Thailand, and Spain. China will decline by 48% since 2017. Meanwhile the US, though in decline by 2100, will actually be more populous in 2100 than 2017.
• The Lancet team estimates several different population trajectories, from its base or "reference" case (shown in blue below) to other cases in which education and contraception advances are either retarded (red) or are sped up (green, purple, and orange). The first chart shows the global trajectory. The next set of ten charts shows the trajectory for the ten most populous nations in the year 2100.

• The team also illustrates in a map the decade in which each nation either already has or is expected to have a TFR under replacement. Note that only six nations, four in sub-Saharan Africa, are not expected to have a sub-replacement TFR by 2100. One of those six, Israel, is expected to remain a social and cultural anomaly (see "Israel's High Fertility Breaks the Rules").

• What accounts for the different trajectories of different nations? Overwhelmingly, changes in fertility. And given the study's reliance on the link between fertility on the one hand and education and contraception availability on the other, fertility in nations like China has a lot further to fall than fertility in nations like the US. Immigration is also a significant driver. Given its high historical rate of immigration and its standard of living advantage, the US is expected to gain a lot more from immigration than most other nations. The following chart illustrates how the China and India are expected to shrink in terms of working-age adults relative to the US over the next century. In 2035, the team expects, China will overtake the US in PPP GDP. But in 2098, it expects the US to again recapture the GDP advantage over China.

• Needless to say, the Lancet team's forecast implies population aging that is even more rapid than in the UNPD model. In 1950, 25 births occurred worldwide for every one person turning 80 years old. By 2100, there will be only one birth for every new 80-year-old. In countries experiencing more than a 25% population decline by 2100, the ratio of 80+ persons to children younger than 15 will grow 9X from 0.17 in 2017 to 1.5 in 2100. Compared to today, the number of Chinese age 20-24 will shrink by nearly two-thirds.

• Overall, I have mixed feelings about the ambitious Lancet project led by professor Murray. I agree with the decision to jettison the UNPD's assumption that fertility rates, as if by a law of nature, must gravitate toward replacement in the long run. I agree that, running current social and cultural trends on autopilot, global population is likely to decline a lot more than what the UNPD projects. And I respect the team's daring willingness to complicate its model by adding in new variables like education, contraception availability, and GDP.
• All that said, I worry that once researchers begin to "endogenize" long-term variables like fertility, they tend to become hopelessly selective in the new assumptions that they presume will drive future events. The researchers believe they have found a stable recent relationship linking fertility to education and contraception. But how can they know if this relationship will remain stable in future decades? And what about all the other developments, predictable or not, that they fail to consider--like nationalism, war, depression, advanced technologies, civil conflict, novel forms of political organization, and new social and religious movements?
• Although the Lancet team boldly introduces GDP per capita into their model, they make no effort to check its living-standard projections against economic plausibility. Even assuming falling fertility, the economy of Nigeria--based mostly on subsistence agriculture--is someday supposed to support a population nearly double the size of the European Union. Hard as it is to say, it is not falling fertility that will cap population growth in sub-Saharan Africa. Rather, it is the Malthusian limit to extreme population density in one of the poorest regions on earth. (See "Africa Expected to Carry World Population Growth.")
• As in Francis Fukuyama's "end of history" scenario, most of the Lancet team's projections assume the continued dominance of a liberal democratic political and cultural model in which greater education and individualism mitigates against births. It is a benign scenario in which which everyone gets richer and has more choices and national borders remain fixed. But what if that model, by generating steep population declines in many societies, results in end-stage vicious cycle effects--such as mounting debt, redundant land and capital stock, grandfather-clause entitlements, declining economic dynamism, the mass emigration of the young, and ultimately displacement or even outright invasion by more demographically expansive neighbors. Might we not expect some competition to displace this model?
• In their conclusion, the authors dismiss the effectiveness of pronatal policies being introduced by authoritarian or Confucian regimes in Central Europe and East Asia. I am not so hasty to dismiss these efforts. If history teaches us anything, it is that the future only belongs to social systems that function. And failure to produce and socialize the next generation of members seems like a pretty clear sign of failure to function. The social competition to overcome such failure is likely to heat up in the decades to come, with results that could rip to shreds any projection we make today. Almost by definition, we can be pretty certain that societies that experience steep demographic decline will in time become irrelevant.
• Let me quote a passage from my book The Graying of the Great Powers. "Demographic change shapes political power like water shapes rock. Up close the force looks trivial, but viewed from a distance of decades or centuries it moves mountains... In AD 900 Berlin had no Germans, Moscow had no Russians, Budapest had no Hungarians, Madrid was a Moorish settlement, and Constantinople had hardly any Turks... Normans had not yet settled in Britain and, before the 16th century, there were no Europeans living in the western hemisphere." As the politically incorrect Mark Steyn accurately remarks in his book America Alone, "Demographics is a game of last man standing."
• So there is part of me that admires the old approach of the UNPD, twenty years ago before they adopted sophisticated modeling and monte carlo simulations. Back then, the UNPD projections were very simple if-then propositions: If fertility and longevity stay to same or go up or down by some clearly defined path, then here are the global population results. You decide the path of inputs. We don't presume to know ourselves.
• There was--and is--a simple humility to this sort of modeling. Rather than adding layer after layer of ambitious and possibly misleading complexity--on the order of Hari Seldon's psychohistorical ten thousand year projection of galactic civilization featured in Isaac Asimov's sci fi--you do the opposite. You cut the complexity back. That way we can all appreciate everything about the future we do not and perhaps cannot know.