I think a lot of the trainees feel they are a cheap source of labor.

我想很多培训生都感觉他们是廉价的劳动力。

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So one way to strengthen the middle class in America is to reform the immigration system so that there is no longer a massive underground economy that exploits a cheap source of labor while depressing wages for everybody else.

WHITEHOUSE: Building a 21st Century Immigration System

By the early 20th century, Haitians had become a source of cheap labor in the neighboring country.

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China is no longer just a cheap source of textile and apparel factory labor but a target market.

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