Gary Becker’s work on “human capital” started around 1960. It was motivated by the rising interest in economic growth at the time. As stated in the introduction to the first edition of his book, Human Capital, “The origin of this study can be traced to the finding that a substantial growth in incomes in the US remains after the growth of physical capital and labor has been accounted for”. This unexplained residual suggested to several researchers that unmeasured features of the quality of the labor force must also be brought into consideration. While econometricians such as Edward Denison, Dale Jorgenson, and Zvi Griliches turned to seek better data that would reduce the scope of the unexplained residual, Becker constructed a detailed and original theory regarding the possible effects of a major unobserved and all inclusive factor, termed, human capital, would have on observed outcomes such as wages and education and their variation over time and among individual types. Most of the theoretical results reported in the three editions of Human Capital, 1964, 1975, and 1995 are already anticipated in a single early paper that was published in the Journal of Political Economy in 1962.