Year	Percent
1990	83.9
1991	84.37
1992	84.99
1993	85.5
1994	85.86
1995	86.18
1996	86.38
1997	86.56
1998	86.54
1999	86.35
2000	86.33
2001	86.27
2002	86.29
2003	86.32
2004	86.33
2005	86.3
2006	86.37
2007	86.43
2008	86.39
2009	86.45
2010	86.51
2011	86.56
2012	86.61
2013	86.66
2014	86.68
2015	86.68
2016	86.53
2017	86.5
2018	86.45
2019	86.24