Year	Percent
1990	86.99
1991	87.02
1992	87.28
1993	87.47
1994	87.57
1995	87.75
1996	87.76
1997	87.83
1998	86.5
1999	84.92
2000	86.06
2001	87.13
2002	88.12
2003	89.02
2004	89.85
2005	89.87
2006	89.93
2007	89.99
2008	90.06
2009	90.11
2010	90.16
2011	90.2
2012	89.97
2013	89.88
2014	89.8
2015	89.75
2016	89.74
2017	89.75
2018	89.82
2019	90.06