Trends in prevalence, demographic characteristics, and severity of children with intellectual disability, 1991–2010^*.

*Proportions and prevalence estimates with numerators <5 children are suppressed due to small sample sizes. Trend analyses reflect weighted prevalence for surveillance years with n<5 children and the subsequent surveillance year (e.g., trend for Hispanic children with ID combined 1991–1992 numerators and denominators for the first time period). Trends in prevalence, demographic characteristics, and severity of children with intellectual disability, 1991–2010*.