Year	Percent
1983	91.43033
1985	91.61946
1987	91.59669
1988	91.3088
1989	91.27917
1990	91.02025
1991	91.33534
1992	90.19178
1993	89.82028
1994	89.24533
1995	88.71724
1996	88.61401
1997	88.47166
1998	88.78679
1999	89.02273
2000	88.84301
2001	88.50023
2002	87.95536
2003	87.8148
2004	87.51751
2005	86.91188
2006	86.33679
2007	85.63907
2008	85.51148
2009	85.12401
2010	83.38847
2011	82.92008
2012	82.6481
2013	81.64428
2014	81.1507
2015	81.35538
2016	81.24653
2017	81.29663