Some unions are pressing for gains in a tight U.S. labor market, pushing employers for higher wages and calling strikes as companies face already snarled supply chains.
A walkout by production workers for farm and construction machinery company Deere & Co. that began Thursday followed recent stoppages at snack producer Mondelez International Inc., commercial truck maker Volvo and breakfast-cereal giant Kellogg Co. Labor leaders elsewhere this year have worked to unionize Starbucks Corp. baristas and Amazon.com Inc. warehouse workers, so far with mixed success.
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