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Crispy beef tacos from Taco Bell Corp. are arranged for a photograph in San Francisco, California, U.S., on Wednesday, March 13, 2013. Taco Bell sales began to pick up last year after its Doritos Locos Tacos mashup generated buzz even among food critics. Photographer: David Paul Morris/Bloomberg via Getty Images

Crispy beef tacos from Taco Bell Corp. are arranged for a photograph in San Francisco, California, U.S., on Wednesday, March 13, 2013. Taco Bell sales began to pick up last year after its Doritos Locos Tacos mashup generated buzz even among food critics. Photographer: David Paul Morris/Bloomberg via Getty Images