Year	Percent
1986	85.6728
1987	85.89794
1988	86.29686
1989	85.49336
1990	85.18857
1991	83.17677
1992	85.23808
1993	84.32143
1994	83.67103
1995	83.88179
1996	83.51178
1997	84.08572
1998	83.37661
1999	83.86854
2000	84.58882
2001	84.57595
2002	84.72797
2003	84.64344
2004	85.93606
2005	85.63172
2006	86.47212
2007	86.65484
2008	86.6795
2009	87.62905
2010	88.26722
2011	89.44662
2012	89.10361
2013	88.35904
2014	89.52917
2015	89.71092
2016	89.61203
2017	90.05261