Year	Percent
1971	0.63742
1972	0.64974
1973	0.66777
1974	0.68562
1976	0.70394
1977	0.70584
1978	0.70679
1979	0.71635
1982	0.74965
1984	0.77164
1986	0.77502
1987	0.77404
1988	0.77709
1989	0.7765
1990	0.78226
1991	0.78501
1992	0.78985
1993	0.79151
1994	0.80248
1995	0.79621
1997	0.80487
1999	0.79744
2000	0.81856
2001	0.81898
2002	0.81989
2003	0.8222
2004	0.85343
2005	0.88979
2006	0.89778
2007	0.90729
2008	0.9269
2009	0.94413
2010	0.94789
2011	0.94989
2012	0.96475
2013	0.97687
2014	0.98046
2015	0.98014