Year	Percent
1991	63.51
1992	63.82
1993	64.59
1994	65.82
1995	66.76
1996	66.56
1997	66.44
1998	66.41
1999	66.78
2000	66.86
2001	66.63
2002	66.35
2003	65.75
2004	65.58
2005	65.95
2006	65.75
2007	65.62
2008	65.9
2009	67.14
2010	68.05
2011	68.42
2012	68.84
2013	69.4
2014	69.84
2015	70.97
2016	71.19
2017	71.68
2018	71.79
2019	71.83
2020	66.32