The facts behind the scary new UN population forecast & those doomster headlines

Summary: A new paper by scientists, using computer models to forecast a dark future — this time about world population. Journalists write a hundred horrific stories, mostly devoid of vital context, most with clickbait headlines. The outer party (America’s professionals and managers) read them for a morning thrill. The Left shivers, confirmed in their certainty of doom unless the world listens to them. The Right mocks. The majority shrugs, apathetic. Here are the facts behind the headlines.

Predicting an ugly future for the world: 11 – 12 billion people in 2100!

New UN population forecast. UN 2012 world population projection: solid red line. The 80% prediction interval (PI): dark shaded area. The 95% PI: light shaded area. The previous UN high and low variants: dashed blue lines. The vertical dashed line marks 2012.

The headlines!

Confident, almost certain, predictions of a crowded Earth and likely a wrecked world: it’s our daily fare from journalists. The Christian Science Monitor says “Global population soars toward 11 billion by 2100. Can Earth support growth?” Newsweek says “World’s Population To Top 11 Billion by 2100“. The Guardian says “Global population set to hit 9.7 billion people by 2050 despite fall in fertility“.

The world now has 7.3 billion people, a load already creating massive environmental damage in the less developed nations — the regions expected to have the greatest population growth.

The paper

The headlines point to “World population stabilization unlikely this century” by Patrick Gerland et al, in Science, 10 October 2014 (ungated copy here) — Abstract…

“The United Nations (UN) recently released population projections based on data until 2012 and a Bayesian probabilistic methodology. Analysis of these data reveals that, contrary to previous literature, the world population is unlikely to stop growing this century.

“There is an 80% probability that world population, now 7.2 billion people, will increase to between 9.6 billion and 12.3 billion in 2100. This uncertainty is much smaller than the range from the traditional UN high and low variants. Much of the increase is expected to happen in Africa, in part due to higher fertility rates and a recent slowdown in the pace of fertility decline. Also, the ratio of working-age people to older people is likely to decline substantially in all countries, even those that currently have young populations.”

The really bad news in the paper

“The main reason for the increase in the projection of the world population is an increase in the projected population of Africa. The continent’s current population of about 1 billion people is projected to rise to between 3.1 and 5.7 billion with probability 95% by the end of the century, with a median projection of 4.2 billion. Although this estimate is large, it does not imply unprecedented population density: Under this projection, Africa’s population density would be roughly equal to that of China today.

“… although fertility has been declining in Africa over the past decade, it has been doing so at only about one-quarter of the rate at which it declined in Asia and Latin America in the 1970s, when these regions were at a comparable stage of the fertility transition …”

Here are their forecasts for each continent, and for Nigeria. Such population growth probably would damage the environment, and devastate Africa. Africa’s wildlife would exist largely as photos, films, and exhibits in zoos. No wonder the headlines were so dark.

World population forecasts by continent.

New UN population forecase for Nigeria.


The Economist replies by putting this forecast in a useful context: “Don’t panic” — Excerpt…

“A UN study sparks fears of a population explosion. The alarm is misplaced. … all such conclusions should come with a big health warning. Forecasting anything 85 years out is highly uncertain — and population projections are no exception. … Three generations will pass between now and 2100. Almost anything could happen in that time.”

In a Wall Street Journal op-ed, Nicholas Eberstadt (Chair of political economy at American Enterprise Institute) said …

“The basic trouble with all long-range population projections is that they are driven by assumptions about birth levels, and there is still no reliable method for predicting fertility levels a generation from now, to say nothing of a century hence. … Global fertility is a matter of human volition, and no computational breakthrough can alter this fundamental fact.”

Experts were quick to reply with more detail, as in these two from the October 31 issue of Science. First, by William Lutz et al of the World Population Program at the International Institute for Applied Systems Analysis: fertility in Africa is unlikely to remain high; it will decline as have all other societies as they modernize (if Africa does not modernize, it cannot support a 4x or 5x population increase).

“The UN assumptions used by Gerland et al. are mainly based on statistical extrapolation, whereas our approach is based on substantive reasoning and assessments of alternative arguments.

“For example, a changing education structure means that young Nigerian women are more educated than their elders, implying likely near-term fertility declines. The UN assumes constant fertility at 6.0 for 2010 to 2015, but the newest Demographic and Health Survey shows that it has already decreased to 5.5 in 2010 to 2013. The population increase for Nigeria from today’s 160 million to 914 million in 2100 expected by the UN is thus unrealistic.

“For China, the UN assumes that fertility will only increase in the future. We assume, like many Chinese scientists and institutions, that it will decline and stay low in the coming decades.”

A second kind of objection came from Robert R. Holt (Prof of Psychology Emeritus, NYU): Africa cannot grow the food to support so many people.

“In their report Gerland et al. omit one of the major determinants of population growth: the food supply. … in their projections of world population growth {they} use as their independent variables only measures of fertility, life expectancy, and age at death … with no mention of agricultural limits. In fact, much of the continent’s area is desert or rain forest (where nutrients are largely stored in living biomass rather than in the soil) and could not be made arable. The agricultural soils that do exist are relatively infertile compared with those of other inhabited continents.”

There is a third kind of objection: politics. Perhaps African states such as Nigeria can become as organized as China to support the projected fantastic population growth, but it’s beyond the ability of demographers to reliably predict. Their failure to do so would allow the four horsemen to limit Africa’s population growth.

Another forecast

The International Institute for Applied Systems Analysis (IIASA) also produces population forecasts using probabilistic techniques. Their most recent publication is “The human core of the shared socioeconomic pathways: Population scenarios by age, sex and level of education for all countries to 2100” by Samir KC and Wolfgang Lutz in Global Environmental Change (in press since July 2014). They convert the SSP storylines used in the IPCC’s AR4 into demographic scenarios. By 2100 world population ranges from 6.9 (SSP1) to 12.6 billion (SSP3).

IIASA has compared their forecast with that of the UNPD. An article by the Wilson Center also compares them, with these conclusions…

The results produced by the two agencies are in turn quite different (see Figure 1). IIASA’s medium variant is aligned with SSP2, which assumes medium fertility, mortality, migration, and education levels in the future and is described as “middle of the road.” In contrast to the UNPD’s forecast of continued growth, it projects that total population will peak around 2070 at 9.4 billion and decline gradually to 9 billion by 2100.

Much of this slowdown in population growth is due to the agency’s education assumptions. The IIASA demographers project the percentage of African women in their peak childbearing years who have attained secondary or higher education will increase from 37 percent in 2010 to 68 percent in 2050.

The demography of the world’s most populous country is also a factor. In National Geographic, Wolfgang Lutz, who directs IIASA’s population program, noted his team’s disagreement with the UNPD projection that China’s fertility rate will rebound from the current rate of 1.6 to 1.9 by 2100; instead they expect it will remain low.

Forecasting with models


The fear bombardment rains on us each day. We lack any way to assess these, let alone put these horrific headlines in a useful broader context. How do they relate to each others? What are their probabilities and magnitudes? How much effort and resources should we spend to prevent or mitigate each? So we grow indifferent and passive, regarding these warnings as little but useful propaganda to further causes we favor (e.g., secular Leftists applauding the Pope as sage for his works on Climate, not on those about abortion and contraception).

The analytical tools that should help us anticipate and prepare for the future — with computer models their most sophisticated expression — have become little but generators for clickbait headlines, giving scientists a chance at 15 minutes of fame. We can do better, and perhaps we must do better.

We can do better. I recommend this first step to protecting the world from its many dangers.

Knowledge + Action is power

For More information

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17 thoughts on “The facts behind the scary new UN population forecast & those doomster headlines”

  1. I’m a lot more worried about Donald Trump than I am about the population of Africa a hundred years from now. A lot of people are. More every day. And the two are not unrelated. Butterfly effect and all that.

    1. Breton,

      Jeb and Clinton are mainstream professional politicians. They will not reform anything, but are unlikely to make terminal errors.

      Trump is an ignorant clown. Although the odds are low that he can win, I and others are disturbed that once again (after Palin) a large fraction of American vote for someone obviously unqualified for the Presidency.

      This suggests a possible rot in the public. History shows that such rots spread rapidly under favorable circumstances.

  2. FM fulminates:

    Confident, almost certain, predictions of a crowded Earth and likely a wrecked world: it’s our daily fare from journalists.

    Since we’re living in a crowded earth and a wrecked world already, FM’s ragegasms against mainstream journalists seems misplaced.

    1. Tom,

      You need to turn off the TV and get out more. Other than a few nations, the world is not “crowded” in any usual sense of the term (some cities are crowded, as always).

      The world is not “wrecked”, and in the developed nations most environmental indicators have been improving for 50 years.

      Yes, there are problems. Some areas have severe problems. And there are many possible futures, some quite dark. But as a description of the present, yours is inaccurate.

  3. World Population Density (click to enlarge)

    World population density (2000)

    Center for International Earth Science Information Network (CIESIN), Columbia University and Centro Internacional de Agricultura Tropical (CIAT). Source: FAO website.

    Look at those light brown areas in the US east and Midwest. From Minnesota down to Louisiana, over to the eastern coastal cities. Drive through those areas and look around: they look almost empty, outside the frequent small towns. Farms and houses, widely separated.

    Much of the eastern US is reverting back to old growth forests, as the farms close and the little towns die. The Catskill forest of eastern NY was almost denuded of trees by 1920. It looks like a giant forest preserve today.

    The light brown of the western US is empty (in terms of density). Many historic sites of the great range wars are now abandoned. The land people fought and died for is almost worthless.

    Much of “flyover” country in the US is not only low-density but becoming more so as the towns die. A large fraction of Midwest towns now have increasingly elderly populations, as they fall below the minimum viable size.

    On a larger time horizon, many of the denser areas of the world have begun demographic collapse. Such as Europe (especially southern Europe) and China, with fertility rates of almost half replacement rate. This is a slow process due to our long life spans, but almost unstoppable.

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