Year	Percent
1983	83.04325
1985	81.89056
1986	82.97295
1987	84.68461
1988	85.22005
1989	84.30779
1990	84.67219
1991	86.34541
1992	85.55054
1993	85.57703
1994	86.2175
1995	85.03567
1996	85.74603
1997	86.45329
1998	86.03689
1999	85.37142
2000	86.98564
2001	87.51427
2002	87.18537
2003	87.89954
2004	89.41043
2005	88.72235
2006	89.09315
2007	89.3304
2008	89.93674
2009	89.35316
2010	89.7872
2011	90.08133
2012	89.92641
2013	89.82796
2014	89.66291
2015	89.45703
2016	89.8761
2017	89.79039