Year	Percent
1990	80.87
1991	80.71
1992	80.23
1993	80.31
1994	80.35
1995	80.34
1996	79.81
1997	78.46
1998	77.75
1999	77.41
2000	77.04
2001	76.99
2002	77.11
2003	77.83
2004	78.58
2005	80.25
2006	80.76
2007	82.39
2008	84.06
2009	85.75
2010	87.4
2011	86.82
2012	86.55
2013	86.68
2014	87.2
2015	87.9
2016	87.3
2017	86.83
2018	86.7
2019	86.81
2020	86.28