Year	%
1983	80.2933
1984	79.95465
1985	79.99389
1986	79.76612
1987	81.11832
1988	77.39211
1989	78.11557
1990	79.08523
1991	80.16967
1992	81.33305
1993	82.46219
1994	83.56191
1995	84.52858
1996	85.50281
1997	86.47032
1998	87.50721
1999	88.39906
2000	87.92575
2001	89.97327
2002	89.7205
2003	89.24502
2004	88.70299
2005	90.0801
2006	91.48029
2007	90.93068
2008	91.19527
2009	91.26529
2010	91.22336
2011	92.08077
2012	90.7652
2013	91.02647
2014	90.7181
2015	91.58179
2016	91.07844
2017	92.09947