Year	Percent
1986	82.66974
1987	82.79365
1988	83.03847
1989	82.51922
1990	82.50719
1991	80.9896
1992	81.60171
1993	81.47212
1994	80.3833
1995	79.77811
1996	79.25691
1997	80.36881
1998	79.60932
1999	80.57593
2000	81.1282
2001	80.66401
2002	80.68797
2003	81.21839
2004	81.9736
2005	82.17716
2006	83.32218
2007	83.15715
2008	83.51771
2009	83.94029
2010	84.67928
2011	85.44332
2012	85.31001
2013	84.82404
2014	85.7934
2015	86.33012
2016	86.32475
2017	86.77477