Bet 510

Duration 40 years (02009-02049)

“Human population of the world will peak at or below 8 billion in the 2040s and then drop dramatically.” Detailed Terms »

Stewart Brand


Brand's Argument

When I made this prediction in August 2009, world population was nearly 6.8 billion. The “medium” prediction from the UN (2008 version) was for a total population of 9.2 billion in 2050, with a gradual decline thereafter. The UN prediction was based in part on the expectation that birthrates in the developed world would RISE to 1.85 children per woman from the present rates that reach as low as 1.1 children per woman in Russia and 1.3 in Italy. Other countries in their category are Spain, Germany, Brazil, Japan, South Korea, and all of Eastern Europe. Some 40% of the world’s countries already have birthrates below replacement level (which is 2.1 children per woman), and in every country the trend continues to be downward.

The overall world birthrate in 2009 was about 2.55 children per woman, and dropping. Because of “population momentum,” when the rate falls below 2.1, total population will keep rising for a while as the young come to childbearing age. But eventually, at any rate below 2.1, total population accelerates downward (just as it accelerated upward when the rate was above 2.1). That’s the effect I expect to play out before mid-century, as the world continues to urbanize and the poor gradually gain enough of an economic foothold to secure their children’s lives and their own old age.

I hope that death rates do not go up, but depending on what happens with climate-change events such as persistent drought and resource wars, there is the possibility of higher death rate in some areas along with the dropping birth rates.

The outcome of this prediction can be decided by figures from the United Nations Population Division. (Context for this prediction may be found on page 60 of my book, Whole Earth Discipline.)

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Detailed Terms

If the United Nations Population Division states that the world population has crossed the 8 billion threshold at any point before 2050, then the Challenger wins this bet.