求翻译：70年代以来，美国华人社会发生了重大的变化，目前，旅美华人已由40年代的10多万猛增至120多万，主要集中在纽约、华盛顿、旧金山、芝加哥、洛杉矶等12个城市。是什么意思？

Since the 1970s, American Chinese society has undergone major changes, at present, Chinese-American from the 1940s soared to more than 100,000 more than 1.2 million, mainly in New York, Washington, San Francisco, Chicago, Los Angeles and other 12 cities.

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Since the 70 's, United States Chinese society has undergone major changes, at present, 40 more than 100,000 Chinese nationals in America have surged to more than 1.2 million, mostly in New York, Washington DC, San Francisco, 12 cities such as Chicago, Los Angeles.

Since the seventies, American Chinese society has changed greatly, at present, the Chinese residing in U.S.A. has already increased to more than 1,200,000 suddenly for more than 100,000 of the forties, mainly centre in 12 cities such as New York, Washington, San Francisco, Chicago, Los Angeles.