Year	Percent
1970	0.81023
1971	0.81712
1972	0.81373
1973	0.8185
1974	0.82797
1975	0.83993
1976	0.84792
1977	0.8636
1978	0.8691
1979	0.87219
1981	0.91107
1982	0.90456
1983	0.89906
1984	0.89448
1985	0.89395
1986	0.89784
1987	0.90795
1988	0.91216
1989	0.92218
1990	0.96426
1991	0.92159
1992	0.93837
1995	0.9411
1996	0.94457
1999	0.94847
2000	0.9471
2001	0.95036
2002	0.95355
2003	0.96287
2012	0.98143
2013	0.98242