Year	% of total
1970	80.33246785971495
1971	80.35285587872445
1972	80.73794201291925
1973	80.69486051130004
1974	80.63976908996375
1975	80.70925572966517
1976	80.962905070782
1977	81.3483177693887
1978	81.3980754382524
1979	81.27742470666998
1980	81.19261560901695
1981	81.74888998410209
1982	81.71801470113017
1983	80.98076211209137
1984	80.41323184290873
1985	79.50160208893267
1986	78.449443008755
1987	77.11860822915324
1988	75.74852079126394
1989	74.41201274398786