Year	% of total
1970	95.85441162412772
1971	95.84072391322907
1972	95.81692681038308
1973	95.81026188203141
1974	95.79300136844749
1975	95.75454740195028
1976	95.77845685130126
1977	95.86780016345095
1978	95.94976309441765
1979	96.1931617600204
1980	96.42019558354978
1981	96.1144898478773
1982	96.77445420134332
1983	96.61432900490438
1984	97.06441736574614
1985	97.32469373837876
1986	97.2913063216988
1987	96.96971757893587
1988	97.03012079694608
1989	97.70514688031075