 According to agricultural researchers Jill Hobbs and Linda Young, writing in 2001, the acquisitions constituted a "major structural change" in the hog industry in the United States, leaving Smithfield in control of 10–15 percent of the country's hog production.As of 2006 four companies—Smithfield, Tyson Foods, Swift & Company, and Cargill—were responsible for the production of 70 percent of pork in the United States.On May 29, 2013, WH Group, then known as Shuanghui Group or Shineway Group, the largest meat producer in China, announced the purchase of Smithfield Foods for $4.72 billion, a sale first suggested in 2009.