Year	%
1970	62.92397
1971	69.94266
1972	78.82774
1973	78.95799
1974	79.64207
1975	80.34679
1976	82.16784
1977	82.59948
1978	84.16104
1979	85.61305
1980	83.76283
1981	87.55443
1982	86.83647
1983	82.37004
1984	83.00865
1985	84.9073
1986	85.11693
1987	85.64557
1988	86.10106
1989	87.41852
1990	88.23678
1991	89.8105
1992	90.77214
1993	89.78525
1994	90.63273
1995	91.02434
1996	91.35883
1997	92.10144
1998	93.10579
1999	93.61434
2000	93.87633
2001	95.00353
2002	94.65302
2003	94.20565
2004	94.23729
2005	94.19233
2006	94.5099
2007	94.37793
2008	94.89482
2009	94.6773
2010	94.6945
2011	94.50022
2012	94.69097
2013	94.80355
2014	94.66321
2015	94.71715
2016	94.78402
2017	94.94487