The number is startling for how large it is. It pops off the page: 440,000 people die each year from preventable errors in hospitals. As shown in the infographic, the Leapfrog Group’s Hospital Safety Score grades more than 2,500 hospitals across the nation on how safe they are for patients. What it shows with the Fall 2015 ranking is sluggish improvement on the safety front; even as some hospitals continue to sustain A ratings year after year, others can’t seem to make the grade.