In 20 of 408 (4.9%) state-years (with Washington, D.C. being treated as a state), the state did not report data about maltreatment to NCANDS, and information on that state is therefore missing in those years. Combined, the 4.9% of state-years missing represent 3.1% of the U.S. population between 2004 and 2011—and far less than that since 2009 (1.4% in 2009 and 1.2% in 2010 and 2011. In missing years, we assumed the state’s cumulative prevalence of confirmed maltreatment shifted in a manner consistent with its relationship to the national estimate. So if a state’s cumulative prevalence was 1.2 times that of the national average in 2005 and missing in 2006, we assumed the state’s cumulative prevalence in 2006 was 1.2 times the national average.
