Year	%
1970	64.956
1971	71.12604
1987	87.04583
1988	87.39493
1989	88.60549
1990	89.43243
1991	90.92373
1992	91.94982
1993	91.13185
1994	91.97076
1995	92.36204
1996	92.70781
1997	93.25023
1998	94.27614
1999	94.67907
2000	94.8273
2001	95.91617
2002	95.43564
2003	94.84026
2004	94.84395
2005	94.86601
2006	95.08369
2007	95.00045
2008	95.51045
2009	95.36767
2010	95.48724
2011	95.38953
2012	95.59825
2013	95.70421
2014	95.54449
2015	95.65876
2016	95.80075
2017	95.97928