Year	%
1973	73.40187
1974	75.71878
1975	79.90173
1976	76.44135
1977	79.14998
1978	72.09305
1979	78.70013
1980	79.84963
1981	80.38635
1982	82.43366
1983	83.64481
1984	83.75806
1985	86.44478
1986	85.30909
1987	85.79789
1988	87.00528
1989	88.56717
1990	87.44825
1991	90.15805
1992	90.15585
1993	90.5587
1994	90.44417
1995	90.19096
1996	90.18754
1997	89.99164
1998	89.80629
1999	90.74146
2000	90.3153
2001	91.94838
2002	93.67949
2003	93.32044
2004	92.4347
2005	91.26417
2006	91.63638
2007	91.91053
2008	92.38894
2009	91.81537
2010	91.5935
2011	91.08068
2012	87.31353
2013	88.14899
2014	88.93071
2015	90.28829
2016	92.12042
2017	92.60509