Year	Percent
1990	87.69
1991	87.71
1992	87.76
1993	87.76
1994	87.9
1995	87.93
1996	87.92
1997	87.93
1998	87.99
1999	88
2000	88.02
2001	87.94
2002	87.87
2003	87.78
2004	87.69
2005	87.61
2006	87.81
2007	87.99
2008	88.18
2009	88.36
2010	88.54
2011	88.72
2012	88.9
2013	88.97
2014	89.06
2015	89.2
2016	89.33
2017	89.49
2018	89.65
2019	89.84