Year	Percent
1990	86.54
1991	86.59
1992	86.65
1993	86.7
1994	86.75
1995	87.97
1996	89.08
1997	89.57
1998	89.02
1999	88.39
2000	88.67
2001	87.58
2002	87.77
2003	87.96
2004	87.7
2005	87.87
2006	87.9
2007	88.41
2008	88.59
2009	88.64
2010	87.91
2011	89.86
2012	89.55
2013	88.11
2014	87.77
2015	87.65
2016	87
2017	86.43
2018	86.81
2019	86.6