Year	Percent
1991	88.52
1992	87.96
1993	87.29
1994	86.6
1995	85.86
1996	85.13
1997	84.33
1998	83.46
1999	82.73
2000	82
2001	81.33
2002	80.65
2003	80.02
2004	79.47
2005	78.98
2006	78.59
2007	78.25
2008	77.94
2009	77.59
2010	77.39
2011	77.26
2012	77.16
2013	77.08
2014	77
2015	77.37
2016	77.67
2017	77.89
2018	78.03
2019	78.09
2020	78.24