Year	%
1972	68.90701
1973	67.21173
1981	70.71916
1982	72.12906
1983	74.76419
1984	72.93915
1985	71.58361
1986	73.5541
1987	74.05818
1991	78.98528
1992	80.15739
1993	80.38775
1996	81.64435
1998	84.33811
1999	83.58062
2000	84.80383
2001	84.36097
2003	87.79891
2004	89.25796
2005	89.36729
2006	88.72992
2007	89.00081
2008	88.88031
2009	89.76702
2010	90.28555
2011	90.86228
2012	90.27885
2013	91.44409
2014	90.91446
2015	91.05032
2016	90.84561
2017	90.81667