 In his teaching he espoused the use of what were at the time increasingly accepted concepts of human capital and rates of return to examine the nature and extent of private and public investments in education and training, in both market and command economies.From the mid-1960s onward, Noah advocated the use of empirical social science methods in comparative education.Much of this work was done in collaboration with his long-standing coauthor, Max A. Eckstein.