Year	Percent
1991	45.84
1992	45.77
1993	46.59
1994	48.9
1995	52
1996	52
1997	52
1998	57.21
1999	53.79
2000	53.79
2001	58.14
2002	58.14
2003	58.14
2004	59.45
2005	60.64
2006	61.85
2007	63.23
2008	63.34
2009	63.41
2010	63.93
2011	63.17
2012	61.55
2013	64.18
2014	64.22