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世界人口从1950年的25亿到1990年的53亿,增加了1倍。其中尤以发展中国家增长较快,而西方国家每对夫妇生育的孩子平均
The world population doubled from 2.5 billion in 1950 to 5.3 billion in 1990. Among them, the growth rate in developing countries is particularly high, while the average number of children born to each couple in Western countries