Year	Percent
1991	67.31
1992	67.31
1993	67.24
1994	67.19
1995	67.16
1996	67.21
1997	67.26
1998	66.84
1999	66.38
2000	65.98
2001	65.49
2002	65.03
2003	64.51
2004	64.04
2005	63.43
2006	62.92
2007	62.36
2008	63.52
2009	64.28
2010	65.22
2011	66.18
2012	66.51
2013	66.76
2014	66.73
2015	65.57
2016	64.98
2017	64.38
2018	64.37
2019	64.3
2020	63.66