Year	Percent
1990	83.19
1991	83.46
1992	83.7
1993	83.99
1994	84.15
1995	84.28
1996	84.41
1997	84.6
1998	84.84
1999	85.14
2000	85.47
2001	85.51
2002	85.63
2003	85.89
2004	86.37
2005	87.01
2006	87.8
2007	88.61
2008	89.27
2009	89.69
2010	89.89
2011	89.78
2012	89.52
2013	89.2
2014	88.93
2015	88.78
2016	88.74
2017	88.84
2018	88.45
2019	88.36