Year	Percent
1991	61.78
1992	61.59
1993	62.01
1994	62.47
1995	62.76
1996	63.02
1997	64.07
1998	63.44
1999	62.66
2000	63.57
2001	63.64
2002	61.63
2003	61.44
2004	61.44
2005	61.97
2006	63.4
2007	64.53
2008	65.53
2009	64.26
2010	65.99
2011	66.43
2012	67.21
2013	67.15
2014	67.98
2015	68.68
2016	68.19
2017	68
2018	68.06
2019	68.33
2020	66.03