By the end of this century, almost every country in the world could have a shrinking population. Although people are living longer due to advances in healthcare and a decline in poverty, they are also having fewer babies. Over the past 50 years, the global fertility rate — the total number of births per woman — has roughly halved to 2.3. In most advanced economies it is already well below the replacement rate of 2.1, where the population replaces itself from one generation to the next, taking into account mortality. Developing nations are on a similar downward trajectory. The upshot is a decline in the working-age population across the developed world, which will bring significant social, economic and political costs if left unaddressed. Some blame a dystopian outlook among millennials and Gen Z — from the harms their children may cause to the climate, to the harms the climate may also do to them. But while a child-free life has gained appeal among some youngsters, for multiple reasons, the vast majority of under-30s in America who do not have kids still want them.
到本世紀(jì)末，全球幾乎所有國家的人口都將減少。盡管醫(yī)療保健的進(jìn)步和貧困人口的減少使人們延長了壽命，但嬰兒數(shù)量也在減少。過去50年里，全球生育率——每名婦女生育的總?cè)藬?shù)——大約減半到2.3。在大多數(shù)發(fā)達(dá)經(jīng)濟(jì)體，該數(shù)字已遠(yuǎn)遠(yuǎn)低于2.1的人口更替率，即考慮到死亡率，人口實(shí)現(xiàn)代際更替的生育率。發(fā)展中國家也處于類似的下行軌道上。