Year	Percent
1990	93.13
1991	93.29
1992	91.94
1993	90.27
1994	88.02
1995	88.38
1996	88.69
1997	87.86
1998	87.41
1999	87.15
2000	88.24
2001	88.92
2002	88.29
2003	89.22
2004	89.03
2005	87.93
2006	87.59
2007	86.88
2008	87.77
2009	87.2
2010	86.96
2011	87.01
2012	87.12
2013	87.18
2014	87.32
2015	87.28
2016	87.58
2017	86.59
2018	86.57
2019	86.54