这是AI给的答案。。

来源: Uusequery 于 2025-05-26 09:16:10 [] [旧帖] [给我悄悄话] 阅读数 : (2760 bytes)
The number of immigrants in the U.S. has fluctuated throughout history, with some periods seeing significantly more immigration than others. In the 1950s, the average was around 250,000 immigrants per year, increasing to an average of 330,000 in the 1960s and 450,000 in the 1970s. The 1980s saw a substantial jump to an average of 735,000, and the 1990s and beyond have seen over 1 million immigrants annually. 
 
 
 
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