Source: Dordick and Wang (1993)
1900 1910 1920 1930 1940 1950 1960 1970 1980 Information 12.4 13.3 19.8 20.9 24.4 27.8 33.1 36.6 38 Services 34 35.7 29.7 27.5 27.3 27.1 26.9 26.7 26.9 Industry 45.4 43.4 43.2 45.2 42.6 39.9 36.1 33.7 31.5 Agriculture 8.2 7.6 7.3 6.4 5.8 5.2 3.9 3 2