Year	Percent
1991	77.98
1992	77.96
1993	77.91
1994	77.86
1995	77.8
1996	77.86
1997	77.9
1998	77.89
1999	77.94
2000	78.03
2001	78.11
2002	77.88
2003	77.64
2004	77.41
2005	77.11
2006	77.77
2007	78.31
2008	78.67
2009	78.93
2010	79.14
2011	79.35
2012	75.82
2013	74.25
2014	72.19
2015	72.11
2016	72.05
2017	71.99
2018	71.9
2019	71.81
2020	71.33