Year	%
1975	91.0183
1976	90.79947
1977	90.73111
1978	91.7165
1979	91.72913
1980	91.95141
1981	92.30448
1982	92.11896
1983	92.18631
1984	92.06318
1985	92.72113
1986	92.26035
1987	92.06018
1988	91.58182
1989	91.8521
1990	92.13297
1991	92.45564
1992	92.65003
1993	93.25655
1994	93.42264
1995	93.91032
1996	94.24891
1997	94.52298
1998	95.18363
1999	95.71812
2000	96.22622
2001	96.75559
2002	97.1015
2003	97.47484
2004	97.52429
2005	97.53583
2006	97.59232
2007	97.58928
2008	97.6657
2009	97.7305
2010	97.89722
2011	97.97591
2012	97.24047
2013	97.67794
2014	98.05445
2015	97.92394
2016	97.99961
2017	97.9885