Year	% of total
1970	92.04840354539543
1971	92.19886068080034
1972	91.98852045547271
1973	91.82166093990801
1974	92.4262239824724
1975	93.54492326131954
1976	93.43401041951827
1977	93.84619631055158
1978	93.75726237420258
1979	93.68739085007752
1980	94.12933399935679
1981	94.16059636917203
1982	94.01152083817296
1983	94.22593184001424
1984	94.09508262965305
1985	93.87838033166014
1986	93.67234159611212
1987	93.685362688595
1988	93.71492702933328
1989	93.74714502341686