Year	Percent
1974	66.82762
1975	68.92511
1976	69.80503
1977	70.92868
1978	74.54884
1979	66.68811
1980	66.19811
1981	72.37565
1982	73.33408
1983	68.95206
1984	72.43764
1985	70.90562
1986	69.78094
1987	69.0812
1988	70.7222
1991	76.13886