Year	Percent
1970	0.57125
1974	0.56682
1975	0.59037
1976	0.59127
1977	0.61353
1984	0.77373
1986	0.78881
1987	0.78997
1988	0.7941
1989	0.79911
1990	0.81168
1991	0.82017
1992	0.82089
1993	0.83555
1994	0.83396
1995	0.84491
1998	0.83676
2012	0.86922