Federal regulators assign a composite rating to each financial institution, based upon an evaluation of financial and operational criteria. The rating is based on a scale of 1 to 5 in ascending order of supervisory concern. "Problem" institutions are those institutions with financial, operational, or managerial weaknesses that threaten their continued financial viability. Depending upon the degree of risk and supervisory concern, they are rated either a "4" or "5". The number and assets of "problem" institutions are based on FDIC composite ratings. Prior to March 31, 2008, for institutions whose primary federal regulator was the OTS, the OTS composite rating was used.