Year	Percent
1990	61.6
1991	63.4
1992	64.1
1993	64.5
1994	64.9
1995	65.3
1996	65.4
1997	65.7
1998	65.6
1999	65.6
2000	68.3
2001	68.3
2003	69.66
2005	66.53
2006	66.79
2007	67.59
2008	68.15
2009	69.87