Richard Baldwin, Rikard Forslid For decades, human capital research has relied on measures of schooling (Mincer 1984, Mankiw et al. 1992). But proxying human capital with schooling assumes that being in school translates into learning. Evidence suggests that this is often not the case (Pritchett 2013). Recent analysis reveals that six out of ten adolescents worldwide cannot meet basic proficiency levels in maths and reading (UNESCO 2017). This gap between schooling and learning is particularly acute in developing countries. In Kenya, Tanzania, and Uganda three quarters of grade 3 students cannot read a basic sentence such as “The name of the dog is Puppy”. In rural India, half of grade 3 students cannot solve a two-digit subtraction problem such as 46 minus 17 (World Bank 2018).