Year	Percent
1990	64.64
1991	64.51
1992	64.41
1993	64.28
1994	64.16
1995	64
1996	63.85
1997	63.77
1998	64.1
1999	64.04
2000	63.92
2001	63.89
2002	63.76
2003	63.64
2004	63.53
2005	63.51
2006	63.37
2007	63.26
2008	62.69
2009	62.96
2010	62.9
2011	64.26
2012	65.46
2013	67.14
2014	67.51
2015	67.81
2016	67.78
2017	68
2018	68.54
2019	68.64