Year	Percent
1991	78.46
1992	78.37
1993	78.11
1994	77.82
1995	77.1
1996	76.34
1997	75.62
1998	74.94
1999	74.02
2000	74.98
2001	76.02
2002	76.93
2003	77.81
2004	78.68
2005	78.52
2006	78.52
2007	78.53
2008	78.49
2009	78.24
2010	78.11
2011	78.09
2012	78.19
2013	78.35
2014	78.51
2015	78.63
2016	78.77
2017	78.84
2018	78.85
2019	78.91
2020	76.28