Federal and state governments share responsibility for ensuring that nursing homes provide quality care in a safe environment for vulnerable elderly or disabled individuals who can no longer care for themselves. States survey nursing homes annually under contract with the Centers for Medicare & Medicaid Services (CMS), the federal agency responsible for ensuring the effectiveness of state surveys. To evaluate state surveyors' performance, CMS conducts federal comparative surveys in which federal surveyors independently resurvey a home recently inspected by state surveyors and compare and contrast the deficiencies identified during the two surveys. Federal comparative surveys can find two types of understatement: (1) missed deficiencies, which can occur when a state surveyor fails to cite a deficiency altogether, or (2) cases where state surveyors cite deficiencies at too low a level. In May 2008, we reported that a substantial proportion of federal comparative surveys conducted from fiscal years 2002 through 2007 identified missed deficiencies that either had the potential to or did result in harm, death, or serious injury to nursing home residents.