Year	Percent
1990	64.1
1991	64.11
1992	64.36
1993	63.93
1994	64.19
1995	64.09
1996	63.98
1997	63.96
1998	63.81
1999	63.81
2000	63.72
2001	63.41
2002	63.53
2003	63.66
2004	64.3
2005	64.59
2006	64.92
2007	65.31
2008	65.37
2009	65.01
2010	65.33
2011	65.75
2012	66.23
2013	66.47
2014	66.74
2015	67.21
2016	67.83
2017	68.43
2018	69.24
2019	70.11