Year	% of total
1970	66.2052455367002
1971	66.01602523159058
1972	65.71912726634183
1973	65.74191073027242
1974	65.36799931804622
1975	65.0895189388968
1976	64.92499696978564
1977	63.951763673899755
1978	65.41139072041858
1979	65.0518766289185
1980	64.53598777249428
1981	64.82637463910548
1982	64.33766968933729
1983	63.637594044823054
1984	63.18478474192225
1985	63.01532110600101
1986	63.71089440938975
1987	63.3241526685028
1988	59.891705237843816
1989	59.55287100305786