Hospitals are making little headway in reducing the frequency at which patients are readmitted despite a government campaign and the threat of financial penalties, according to Medicare data released Thursday. More than one in five Medicare patients are returning to the hospital within a month of discharge. "We've put all of this policy effort into this area, and yet we're seeing no movement," said Ashish Jha, a professor at the Harvard School of Public Health. "Either we have no idea how to really improve readmissions, or most of the readmissions are not preventable and the efforts being put on it are not useful."