Source: Dordick and Wang (1993).
1900 1910 1920 1930 1940 1950 1960 1970 1980
Information 12.8 14.9 17.7 24.5 24.9 30.8 42 46.4 46.6
Services 25.1 17.7 17.8 19.8 22.5 19 17.2 21.9 28.8
Industry 26.8 36.3 32 35.3 37.2 38.3 348 28.6 22.5
Agriculture 35.3 31.1 32.5 20.4 15.4 11.9 6 3.1 2.1