Year	Percent
1990	88.15
1991	87.72
1992	87.27
1993	86.8
1994	86.26
1995	85.9
1996	86
1997	86.18
1998	86.46
1999	86.75
2000	87.05
2001	87.67
2002	88.24
2003	88.78
2004	89.19
2005	89.5
2006	89.52
2007	89.49
2008	89.57
2009	89.48
2010	89.4
2011	89.15
2012	88.98
2013	88.95
2014	88.54
2015	88.67
2016	88.71
2017	88.89
2018	88.84
2019	88.93