Year	%
1973	74.53775
1974	76.7572
1975	80.63017
1976	77.32789
1977	79.96256
1978	73.26445
1979	79.58109
1980	80.72776
1981	81.31129
1982	83.26743
1983	84.43234
1984	84.51053
1985	86.96261
1986	85.8652
1987	86.25626
1988	87.45359
1989	88.93835
1990	87.9385
1991	90.46893
1992	90.50726
1993	90.92096
1994	90.84706
1995	90.6048
1996	90.61515
1997	90.43868
1998	90.27722
1999	91.14127
2000	90.77378
2001	92.25361
2002	93.81263
2003	93.50953
2004	92.69579
2005	91.6396
2006	91.9986
2007	92.24784
2008	92.69742
2009	92.21464
2010	91.99418
2011	91.60468
2012	88.61763
2013	89.54742
2014	89.48333
2015	90.20035
2016	91.28945
2017	91.86994