Year	Percent
1971	0.76435
1973	0.76926
1974	0.7728
1975	0.76043
1976	0.75271
1977	0.75087
1978	0.75188
1979	0.75636
1980	0.76549
1981	0.76434
1982	0.7656
1983	0.75491
1984	0.75034
1985	0.74245
1987	0.75699
1988	0.76753
1989	0.7781
1990	0.78068
1995	0.83994
1999	0.88596
2000	0.89699
2001	0.91021
2002	0.91139
2003	0.91313
2004	0.90244
2005	0.91514
2006	0.9342
2007	0.94334
2008	0.94662
2009	0.94473
2011	0.95717
2012	0.96093
2013	0.96527
2014	0.97741
2015	0.98207
2016	0.9975
2017	0.99887