Year	Percent
1990	88.28
1991	88.05
1992	87.59
1993	87.36
1994	87.13
1995	86.95
1996	86.86
1997	86.36
1998	86.19
1999	86.13
2000	85.91
2001	85.89
2002	85.77
2003	85.96
2004	86.28
2005	87.31
2006	88.68
2007	90.05
2008	90.73
2009	91.19
2010	91.93
2011	92.3
2012	92.54
2013	92.74
2014	92.94
2015	93.14
2016	93.03
2017	92.92
2018	92.87
2019	92.87