GOLDIN, CLAUDIA; KATZ, LAWRENCE F. - In: The Journal of Economic History 60 (2000) 03, pp. 782-818
We present the first estimates of the returns to years of schooling before 1940 using a large sample 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....