Year	Percent
1991	79.25
1992	79.66
1993	79.94
1994	80.14
1995	80.3
1996	80.38
1997	80.44
1998	80.33
1999	80.06
2000	79.94
2001	79.75
2002	79.57
2003	79.43
2004	79.31
2005	79.17
2006	79.15
2007	79.12
2008	78.99
2009	78.78
2010	78.69
2011	78.61
2012	78.52
2013	78.45
2014	78.44
2015	78.47
2016	78.43
2017	78.53
2018	78.64
2019	78.57
2020	77.01