About 20 million migrant workers at factories and construction sites have already lost their jobs, according to government s estimates.

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This is partly because many of these job losses have been in industries such as toymaking, textiles and construction, which use migrant and unskilled workers.

ECONOMIST: Business in Asia

Perhaps the most rapid change has taken place in North Carolina, where a technology and construction boom has sucked in hundreds of thousands of migrant workers, swelling the Hispanic population by more than 1, 000% since 1990.

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While the number of migrant workers in China rose 3.9% last year, manufacturers face stiff competition from construction, mining and other industries for staff.

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