Year	Percent
1990	81.28
1991	81.28
1992	81.26
1993	81.21
1994	81.09
1995	81
1996	80.84
1997	80.68
1998	80.49
1999	80.29
2000	80.06
2001	79.85
2002	79.61
2003	79.35
2004	79.08
2005	78.81
2006	78.62
2007	78.44
2008	78.28
2009	78.16
2010	78.07
2011	78.09
2012	78.15
2013	78.21
2014	78.26
2015	78.29
2016	78.24
2017	78.2
2018	78.16
2019	78.15
2020	77.33