America's Census Bureau simply assumes that current fertility rates will persist.

美国人口普查局作出简单假设，目前的生育率将持续一段时间。

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The target reductions in fertility rates were reached long ago. Current rates, he says, are below replacement levels and are unsustainable.

他说，生育率的下降目标早已实现，现在的生育率已经低于人口替换率，这会导致失衡。

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Stabilization of the world population at 8 billion or below by 2050, through a voluntary reduction of fertility rates, rather than the current trajectory of more than 9 billion by midcentury

2050年将世界人口稳定在80亿或80亿以下。 通过自发主动减少出生率，将改变人口以现在的增长速度在本世纪中叶突破90亿的推测。

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By 2050 there will be 35 persons of retirement age for every 100 working-age individuals in the U.S. at current fertility levels, according to the UN.

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The 20 countries where fertility is at or below the level needed to sustain the current population include China, Hong Kong, Macao, North Korea, Iran, Kazakhstan, Singapore, Thailand, Armenia, Cyprus, Georgia, Barbados, Cuba, Guadeloupe, Martinique, Puerto Rico, Saint Lucia, Trinidad and Tobago and Chile.

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If Russia continues to make progress in reducing mortality and if not increasing fertility then at least preventing it from declining, it will likely be able to maintain its current population.

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