Year	Percent
1991	75.74
1992	75.69
1993	75.51
1994	75.27
1995	75.12
1996	74.84
1997	74.51
1998	74.15
1999	73.72
2000	73.36
2001	72.57
2002	71.78
2003	71.15
2004	70.64
2005	70.33
2006	70.73
2007	71.18
2008	71.7
2009	71.9
2010	72.28
2011	72.79
2012	73.25
2013	73.69
2014	73.79
2015	74.14
2016	74.08
2017	74.19
2018	74.08
2019	73.94
2020	68.52