Year	% of total
1970	0.8476961816670072
1971	0.8912254160579709
1972	0.9261591320479984
1973	0.9370831127743128
1974	0.9449619345962066
1975	0.9584872875049527
1976	0.9806987619897292
1977	0.9858947127488754
1978	0.9945901734306304
1979	0.99065457645961
1980	1.004187666580213
1981	0.9753064531792729
1982	0.9393926239080311
1983	0.8400291704624218
1984	0.779996733073495
1985	0.7131686401547118
1986	0.6514789957769686
1987	0.5884090017556939
1988	0.5264931699106509
1989	0.4656659994574916