Year	Percent
1990	87.85
1991	87.85
1992	87.82
1993	87.78
1994	87.75
1995	87.73
1996	87.77
1997	87.81
1998	87.85
1999	87.88
2000	87.89
2001	87.93
2002	87.99
2003	87.97
2004	87.94
2005	87.89
2006	88.51
2007	89.07
2008	89.57
2009	89.99
2010	90.34
2011	89.98
2012	89.56
2013	89.03
2014	88.41
2015	87.69
2016	87.52
2017	87.38
2018	87.26
2019	87.15