The world’s largest retailer said it would raise health insurance premiums for its entire U.S. In addition, Wal-Mart will end coverage for employees who work fewer than 30 hours a week, a change that will impact 2 percent of U.S. Starting then, companies with 50 or more employees will have to offer health insurance to those working at least 30 hours a week, a mandate that has drawn criticism from some companies worried about higher costs. Wal-Mart, which announced the change in a blogpost on Tuesday, had cited health care expenses as a problem in August, when it cut its 2014 profit forecast.