Year	Percent
1971	0.61873
1972	0.61974
1973	0.62068
1974	0.62409
1975	0.61841
1976	0.63034
1977	0.63886
1978	0.64498
1979	0.65739
1980	0.66307
1981	0.67907
1982	0.69211
1983	0.70749
1984	0.72552
1985	0.74366
1986	0.76128
1987	0.77398
1988	0.76407
1989	0.79868
1990	0.81638
1991	0.82348
1992	0.85558
1993	0.86282
1994	0.85101
1995	0.88575
1996	0.81124
1997	0.87683
1999	0.92312
2000	0.93286
2001	0.94193
2003	0.95054
2004	0.95747
2009	0.97591
2010	0.97114
2011	0.96893
2012	0.9852
2013	0.9855
2014	0.99562
2016	0.99274