Year	Percent
1990	86.58
1991	86.6
1992	86.57
1993	86.53
1994	86.5
1995	86.49
1996	86.52
1997	86.56
1998	86.59
1999	86.61
2000	86.63
2001	86.66
2002	86.73
2003	86.7
2004	86.68
2005	86.63
2006	87.24
2007	87.78
2008	88.27
2009	88.7
2010	89.05
2011	88.73
2012	88.35
2013	87.84
2014	87.24
2015	86.54
2016	86.35
2017	86.19
2018	86.05
2019	85.92
2020	83.45