Year	%
1970	63.39238
1971	69.90533
1972	79.22554
1973	79.30267
1974	79.92385
1975	80.52974
1976	82.37197
1977	82.82329
1978	84.26349
1979	85.69444
1980	84.0271
1981	87.67551
1982	87.03231
1983	82.84244
1984	83.42944
1985	85.24749
1986	85.43254
1987	85.91015
1988	86.31405
1989	87.54775
1990	88.35194
1991	89.84998
1992	90.76516
1993	89.82787
1994	90.63768
1995	91.01546
1996	91.32983
1997	91.86079
1998	93.00428
1999	93.50397
2000	93.71352
2001	94.7788
2002	94.42434
2003	93.97078
2004	93.97713
2005	94.08784
2006	94.39365
2007	94.32395
2008	94.78042
2009	94.58311
2010	94.62379
2011	94.48381
2012	94.69027
2013	94.81804
2014	94.7036
2015	94.75882
2016	94.82882
2017	94.98372