Year	Percent
1991	63.95
1992	64.06
1993	64.31
1994	64.64
1995	64.98
1996	64.7
1997	64.48
1998	64.46
1999	64.7
2000	65.16
2001	65.21
2002	65.48
2003	66.1
2004	66.94
2005	67.88
2006	68.26
2007	68.89
2008	69.7
2009	70.62
2010	71.4
2011	70.57
2012	70.62
2013	70.62
2014	70.65
2015	70.7
2016	71.07
2017	71.56
2018	72.06
2019	72.44
2020	69.67