Environment & Energy

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Thanks to a phenomenon known as population momentum, a youthful population with constant levels of mortality and a net migration¹ of zero continues to grow even when fertility remains constant at the replacement level.² In this situation, a relatively youthful age structure promotes a more rapid growth, because the births being produced by the relatively large number of women of reproductive age outnumber the deaths occurring in the total population, even if the fertility of the average woman stands at the replacement level.

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Under the assumptions of the momentum variant, the world’s population would continue to increase in the coming years and decades, reaching 8.3 billion in 2030 and 8.9 billion in 2050. Thereafter, the global population would stabilize at around 9 billion. Compared to an estimate of around 7.4 billion for 2015, an additional 1.5 billion persons would thus be added to the world’s population by 2050, even if fertility were to reach the replacement level instantly and if mortality were to remain constant at levels observed in 2010-2015.

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