Year	Percent
1990	85.67
1991	85.63
1992	86.2
1993	86.56
1994	86.48
1995	86.51
1996	86.44
1997	86.46
1998	87.33
1999	85.97
2000	85.48
2001	86
2002	86.74
2003	86.14
2004	85.73
2005	85.22
2006	86.09
2007	87.05
2008	88.69
2009	88.42
2010	88.61
2011	88.04
2012	88.43
2013	87.65
2014	87.2
2015	87.58
2016	87.85
2017	88.56
2018	89.03
2019	88.33