Year	% of total
1970	89.18907126883778
1971	88.89107268594282
1972	88.63440173572958
1973	88.19530321031357
1974	86.82435982675415
1975	86.8211092566769
1976	86.43979847257964
1977	86.91617563632087
1978	86.49645463789567
1979	86.01617885414787
1980	83.793896596759
1981	83.980716866131
1982	83.7346159526111
1983	86.27680991836897
1984	86.589644671646
1985	86.45869403711399
1986	86.25822533051458
1987	86.20795747080972
1988	85.72641325622253
1989	83.153271167501