Year	%
1973	70.35166
1974	72.33027
1975	75.85976
1976	73.64916
1977	75.91675
1978	70.02772
1979	75.30328
1980	76.77346
1981	77.71997
1982	79.73244
1983	80.4164
1984	79.21761
1985	81.48682
1986	80.55848
1987	81.35008
1988	82.02697
1989	83.33419
1990	82.79667
1991	85.56269
1992	86.46401
1993	87.14202
1994	87.37684
1995	87.64026
1996	88.28749
1997	88.59316
1998	88.89482
1999	89.95266
2000	90.11433
2001	90.76096
2002	92.00782
2003	93.06603
2004	89.04745
2005	87.70689
2006	90.47126
2007	90.86168
2008	90.65567
2009	90.01584
2010	89.55045
2011	88.84311
2012	85.02709
2013	85.77699
2014	86.63735
2015	88.11387
2016	90.00013
2017	90.56908