Year	%
1970	93.41408
1971	93.38377
1972	93.746
1973	93.98661
1974	94.37583
1975	95.19305
1976	95.17942
1977	95.71715
1978	96.11785
1979	96.33158
1980	96.74198
1981	96.55547
1982	96.4194
1983	96.79481
1984	97.05951
1985	97.41707
1986	97.3255
1987	97.17006
1988	97.1878
1989	97.30079
1990	97.39983
1991	97.48452
1992	97.41932
1993	97.31559
1994	97.00071
1995	97.26669
1996	97.39489
1997	97.25684
1998	97.45818
1999	97.53207
2000	97.70094
2001	97.65357
2002	97.65959
2003	97.61841
2004	97.63064
2005	97.70796
2006	97.67152
2007	97.83942
2008	97.83169
2009	97.831
2010	97.85206
2011	97.90427
2012	98.05185
2013	97.99617
2014	97.90584
2015	97.58464
2016	97.32294
2017	97.3834