Year	Percent
1970	0.81075
1971	0.82581
1972	0.82981
1973	0.82858
1974	0.84302
1975	0.84594
1976	0.85063
1977	0.85354
1978	0.84139
1979	0.83981
1980	0.84258
1981	0.84963
1982	0.86615
1983	0.85659
1993	0.8676
1996	0.86563
1998	0.87705
1999	0.86824
2000	0.89869
2001	0.9062
2002	0.91286
2004	0.92526
2005	0.93206
2006	0.93975
2007	0.94784
2008	0.95558
2009	0.96545
2010	0.9674
2011	0.96807
2012	0.96535
2013	0.96103
2014	0.96287
2015	0.95962
2016	0.96038