Prevalence and Trends of Developmental Disabilities among Children in the United States: 2009–2017 Benjamin Zablotsky, Lindsey I. Black, Matthew J. Maenner, Laura A. Schieve, Melissa L. Danielson, Rebecca H. Bitsko, Stephen J. Blumberg, Michael D. Kogan and Coleen A. Boyle Commentary Increasing Prevalence of Developmental Disabilities Among Children in the US: A Sign of Progress? Maureen S. Durkin