I think it was partly the New Deal legislation that made it very strong in the United States.

我觉得部分上是因为罗斯福新政,使得30年期限在美国非常流行

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Because of the wide spread belief that it was the new deal which saves the country and got us out of the depression.

因为大家普遍都这样认为,是新政,救了美国,让我们脱离经济衰退。

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