Is early childhood really that important for adult life?

How important are the preschool years for adult outcomes? Empirical evidence from rich countries mostly shows that treatments during preschool years persist to adult years. James Heckman, for example, has pushed very hard this result. How robust is it once you look at more extreme cases?

Todd Schoellman does this by looking at refugees from Indochina who arrived in the US. He finds no difference in adult wages, education and anything else he can throw at the data between refugees who arrived in the United States at different preschool ages (before 5). One would have expected a huge effect, as they were exposed to very dire environments in their home countries or the refugee camps. It runs also counter to other empirical evidence and standard models. So what is going on here? Schoellman argues that what really matters in early childhood were the parents, much less the environment. That result changes somewhat once the arrival date falls into school age.