Northwest Airlines announced Friday it would cut 10, 000 jobs, nearly a fifth of its work force.

CNN: Airlines reeling, laying off thousands

Immigrants make up nearly one-fifth of the work force, mainly in agricultural and unskilled jobs.

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Last week, Pfizer raised earnings forecasts slightly but also announced it would lay off more than 2, 000 salespeople, a fifth of its marketing force.

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Temporary and part-time workers, with little training and few career prospects, have increased from one-fifth to one-third of the labour force over the past 20 years.

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The Force India duo of Paul Di Resta and Adrian Sutil will start fifth and sixth respectively, while Lotus' Kimi Raikkonen -- who was fastest in Friday's practice sessions -- will be eighth.

CNN: Rosberg claims surprise pole position in Bahrain