Year	Percent
1991	90.49
1992	89.76
1993	88.74
1994	87.8
1995	86.47
1996	86.4
1997	86.11
1998	85.78
1999	85.4
2000	85.04
2001	84.81
2002	84.58
2003	84.39
2004	84.24
2005	84.11
2006	84.02
2007	83.96
2008	83.9
2009	83.71
2010	83.58
2011	83.47
2012	83.33
2013	83.16
2014	83
2015	82.96
2016	82.89
2017	82.88
2018	82.83
2019	82.73
2020	79.24