Standard & Poor’s, the world’s largest rating agency, announced a broad overhaul of its rating system yesterday, in response to criticism that it was too lenient in grading subprime-mortgage-backed securities. Its critics weren’t mollified. S&P’s “piecemeal changes” look “more like public relations window dressing than systemic reform,” said New York Attorney General Andrew Cuomo, who is investigating the agencies. (The Washington Post, free registration)