A Volkswagen 2016 Touareg TDI is seen at a VW dealership.

A Volkswagen 2016 Touareg TDI is seen at a VW dealership.  Volkswagen shares plunged more than 20 percent on Monday, their biggest ever one-day fall, after news that the German carmaker had rigged U.S. emissions tests. 

Credit:

Shannon Stapleton/Reuters

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