Year	Percent
1991	81.47
1992	81.03
1993	80.94
1994	80.69
1995	80.52
1996	80.66
1997	80.95
1998	81.11
1999	81.34
2000	82.2
2001	82.72
2002	82.98
2003	82.92
2004	82.93
2005	82.92
2006	82.88
2007	82.81
2008	82.71
2009	82.85
2010	83.05
2011	82.98
2012	83.16
2013	83.36
2014	83.37
2015	83.37
2016	83.36
2017	83.34
2018	83.32
2019	83.34
2020	83.17