Quoting the study "Geographic choices were important: first-generation immigrants were more likely to settle in areas with higher mobility prospects for their children. When we compare children growing up in the same US region, the intergenerational gap between immigrants and the US-born is reduced by 70%. When comparing children growing up in the same county, we no longer find an intergenerational gap between the children of immigrants and US-born individuals. In other words, immigrant children did not earn more than others who grew up in the same location. Rather, their parents chose to live in locations that offered high mobility prospects to all."