As unions demand higher wages for autoworkers in cities such as Detroit, automobile manufacturers are slowly expanding operations in Mexico in an effort to reduce costs. Recently, General Motors announced that it would invest $350 million in facilities in Mexico to produce the new Chevrolet Cruze sedans. The company announced that these plans would not affect U.S. facilities that will also be manufacturing the same vehicle.
See "U.S. Autoworkers Face Threat as Car Makers Drawn to Mexico", The New York Times, March 25, 2015