Year	Percent
1991	70.65
1992	70.64
1993	70.84
1994	66.73
1995	64.53
1996	62.93
1997	62.69
1998	62.61
1999	62.2
2000	62.27
2001	63.32
2002	63.68
2003	63.7
2004	63.43
2005	63.87
2006	64.29
2007	64.92
2008	65.68
2009	65.46
2010	66.3
2011	66.59
2012	66.75
2013	66.94
2014	67.29
2015	67.4
2016	66.65
2017	65.85
2018	65.75
2019	65.51
2020	62.06