Andrew Bershadker & Robert H Haveman 
Human Capital in the United States from 1975 to 2000 [PDF ebook] 

This study enhances the existing measures of the nation’s human capital and the extent to which that capital is utilized. Haveman, Bershadker, and Schwabish develop an indicator of the value of the human capital stock held by the nation’s working-age population called Earnings Capacity (EC), and use it to study the time trends in aggregate human capital in the United States and human capital per worker. They also use EC to evaluate utilization of the nation’s human capital stock, thereby demonstrating the usefulness of the EC indicator in measuring the size and strength of the U.S. economy.