Year	Percent
1990	89.67
1991	89.53
1992	89.49
1993	89.44
1994	89.33
1995	89.23
1996	88.62
1997	88.56
1998	88.49
1999	88.5
2000	88.43
2001	88.33
2002	88.16
2003	87.93
2004	87.73
2005	88.22
2006	88.08
2007	87.74
2008	87.29
2009	87.64
2010	87.82
2011	88.01
2012	88.34
2013	89.05
2014	88.77
2015	88.61
2016	88.89
2017	89.06
2018	89.29
2019	89.08