Year	Percent
1990	82.97
1991	82.8
1992	82.83
1993	82.82
1994	82.83
1995	82.9
1996	82.82
1997	82.81
1998	82.81
1999	82.83
2000	82.91
2001	82.76
2002	82.76
2003	82.69
2004	82.72
2005	82.7
2006	82.62
2007	82.58
2008	82.55
2009	82.53
2010	82.53
2011	82.44
2012	82.44
2013	82.43
2014	82.39
2015	82.09
2016	81.4
2017	80.64
2018	80.72
2019	80.82