Education and Income in the Early Twentieth Century: Evidence from the Prairies
利用1915年爱荷华州人口普查数据，首次估计了1940年前教育年限的回报率，发现高中或大学教育回报率约为11%，且教育能帮助进入高薪白领工作，但职业内部也存在显著工资差异。
We present the first estimates of the returns to years of schooling before 1940 using a large sample of individuals (from the 1915 Iowa State Census). The returns to a year of high school or college were substantial in 1915—about 11 percent for all males and in excess of 12 percent for young males. Education enabled individuals to enter lucrative white-collar jobs, but sizable educational wage differentials also existed within occupational groups. Returns were substantial even for those in farming. We find, using U.S. census data, that returns to education decreased between 1915 and 1940 and again during the 1940s.