Year	%
1970	61.64092
1971	68.74849
1972	78.31981
1973	78.22792
1974	78.7461
1990	87.0914
1992	89.48472
1993	88.44077
1994	89.21988
1995	89.56406
1996	89.91316
1997	90.41805
1998	91.67646
1999	92.26677
2000	92.55391
2001	93.60811
2002	93.37839
2003	93.06456
2004	93.11163
2005	93.32583
2006	93.74288
2007	93.68892
2008	94.10863
2009	93.83781
2010	93.79509
2011	93.58975
2012	93.79521
2013	93.9385
2014	93.87317
2015	93.86144
2016	93.8564
2017	93.99431