The memo describes the methods used to derive an estimate of the economic benefits of high-quality universal preschool over the lifespan of a cohort of students. This analysis has four steps: 1. Calculate total costs of high-quality universal preschool for a cohort of 4-year-old children, by state. 2. Calculate total benefits of high-quality universal preschool for a cohort of 4-year-old children, by state. 3. Calculate net benefits of high-quality universal preschool, by state. 4. Add together individual states' net benefits to calculate national estimate of net benefits of preschool. This memo also describes a preliminary analysis used to calculate the difference between potential net benefits of universal preschool--as described above--and current net benefits. (author abstract)