这就是人口更替水平。
美国有一个大问题,那就是正在发生的人口更替过程。
America has a big problem, a population replacement process in progress.
他解释说,1950年总生育率为5.8,而1980年巨幅下降至2.3,略微高于人口更替水平的底线。
The total fertility rate had been 5.8 in 1950, he notes, and had declined sharply to 2.3 by 1980, just above replacement level.
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