Year	Percent
1990	84.49
1991	84.29
1992	83.82
1993	83.77
1994	83.51
1995	83.31
1996	83.47
1997	83.8
1998	83.98
1999	84.26
2000	85.2
2001	85.78
2002	86.1
2003	86.04
2004	86.02
2005	85.97
2006	85.86
2007	85.74
2008	85.61
2009	85.97
2010	85.85
2011	85.46
2012	85.38
2013	85.37
2014	85.38
2015	85.39
2016	85.38
2017	85.35
2018	85.32
2019	85.34