Year	Percent
1991	84.47
1992	84.47
1993	84.43
1994	84.43
1995	84.42
1996	84.46
1997	84.49
1998	84.49
1999	84.46
2000	84.49
2001	84.53
2002	84.75
2003	84.97
2004	85.2
2005	85.43
2006	85.68
2007	85.6
2008	85.42
2009	85.02
2010	84.07
2011	83.06
2012	82.66
2013	82.19
2014	82.09
2015	82.08
2016	82.02
2017	81.97
2018	81.89
2019	81.78
2020	81.37