Year	Percent
1990	65.41
1991	65.11
1992	64.8
1993	64.5
1994	64.19
1995	63.89
1996	63.58
1997	63.28
1998	62.98
1999	62.67
2000	62.37
2001	62.02
2002	61.67
2003	61.32
2004	60.98
2005	60.63
2006	60.43
2007	60.23
2008	60.03
2009	59.84
2010	59.64
2011	59.52
2012	59.4
2013	59.28
2014	59.17
2015	59.05