But despite this rapid growth [in technical occupations], what is remarkable is the concentration of technical expertise of United States industries in a relatively small grouping.  Taken together, the technical engineers, chemists, scientists, architects, draftsmen, designers, and technicians represent not much more than 3 percent of the total labor force in 1970…On balance, it is probably proper to say that the technical knowledge required operate the various industries of the United States is concentrated in a grouping in the neighborhood of only 3 percent of the entire working population--although this percentage is higher in some industries and lower in others (166-7).