Year	Percent
1990	59.6
1991	59.1
1992	58.4
1993	57.4
1994	57.2
1995	57
1996	57.2
1997	57.3
1998	59.2
1999	59.6
2000	60.6
2001	61.2
2002	62.2
2003	62.95
2004	63
2005	64.59
2006	65.05
2007	64.04
2008	64.61
2009	64.94