Year	Percent
1990	66.04
1991	65.95
1992	65.87
1993	65.78
1994	65.7
1995	65.61
1996	65.53
1997	65.44
1998	65.36
1999	65.27
2000	65.19
2001	64.93
2002	64.83
2003	64.75
2004	64.67
2005	64.58
2006	64.5
2007	64.4
2008	64.26
2009	64.15
2010	63.99
2011	63.91
2012	63.76
2013	63.6
2014	63.52
2015	63.44