The Leapfrog Group, a watchdog organization, has come out with its Hospital Safety Grade, ranking states by the safety of their hospitals. Delaware, North Dakota, and the District of Columbia tied for last place, while New Jersey topped the list, as nearly 57 percent of its hospitals received an A grade. Oregon, Virginia, Massachusetts, and Texas rounded out the top five. Leapfrog assigns letter grades to 2,600 U.S. hospitals every six months, and tends to evaluate hospitals more critically than the Centers for Medicare and Medicaid Services, which rate about 90 percent of U.S. hospitals as “average,” according to the Delaware News Journal. The organization’s grades are based on the number of medical errors, injuries and infections, responses from patient surveys, and data from the American Hospital Association. According to Leapfrog, about 440,000 preventable deaths occur in hospitals every year.