Year	Percent
1990	81.56
1991	81.65
1992	82.68
1993	82.39
1994	82.83
1995	85.67
1996	84.24
1997	83.41
1998	85.17
1999	86.58
2000	88.37
2001	88.3
2002	86.88
2003	86.69
2004	86.29
2005	85.68
2006	86.67
2007	86.7
2008	85.76
2009	84.1
2010	84.36
2011	84.16
2012	84.52
2013	85.56
2014	87.02
2015	88.09
2016	89.09
2017	88.35
2018	87.08
2019	86.67