Year	Percent
1990	63.13
1991	62.68
1992	62.23
1993	61.77
1994	61.32
1995	60.87
1996	60.42
1997	59.97
1998	59.52
1999	59.07
2000	58.61
2001	58.16
2002	57.71
2003	57.26
2004	56.81
2005	56.36
2006	55.9
2007	55.45
2008	55
2009	54.55
2010	54.1
2011	53.68
2012	53.26
2013	52.84
2014	52.42
2015	52