Year	Percent
1983	90.46196
1984	89.60409
1985	89.39345
1986	89.3404
1987	88.0871
1988	87.8907
1989	86.66967
1990	86.56999
1991	86.95128
1992	87.2733
1993	87.336
1994	87.01296
1995	87.07938
1996	87.45122
1997	87.60613
1998	87.99606
1999	87.8176
2000	88.1504
2001	88.17101
2002	88.0874
2003	87.58354
2004	87.28366
2005	87.42324
2006	87.17125
2007	86.9842
2008	86.88324
2009	86.69277
2010	86.26881
2011	86.15046
2012	85.41927
2013	85.36136
2014	84.96411
2015	85.1748
2016	84.7904
2017	84.90585