The 2009 Washington Legislature directed the Institute to “calculate the return on investment to taxpayers from evidence-based prevention and intervention programs and policies.” The Legislature instructed the Institute to produce “a comprehensive list of programs and policies that improve . . . outcomes for children and adults in Washington and result in more cost-efficient use of public resources.” The Legislature authorized the Institute to receive outside funding for this project; the MacArthur Foundation supported 80 percent of the work and the Legislature funded the other 20 percent. This main report summarizes our findings. Readers can download the two detailed technical appendices for in depth results and statistical methods.