Year	Percent
1990	58.9
1991	59.2
1992	59.7
1993	60
1994	61.6
1995	63.3
1996	63.8
1997	63.8
1998	63.8
1999	63.8
2003	51.74
2004	52.87
2005	55.62
2006	54.34
2007	56.16
2008	56.54
2009	57.56