Year	Percent
1991	83.26
1992	83.57
1993	83.87
1994	84.2
1995	84.5
1996	84.8
1997	85.13
1998	85.43
1999	85.74
2000	86.07
2001	86.37
2002	86.67
2003	87
2004	87.3
2005	87.61
2006	87.61
2007	87.61
2008	87.61
2009	87.61
2010	87.61
2011	87.61
2012	87.61
2013	87.61
2014	87.61
2015	87.62