Year	Percent
1990	75.4
1991	75.3
1992	78.8
1996	75.8
1997	76.5
1998	76.9
1999	77.4
2000	77.6
2001	75.3
2002	78.9
2003	79.13
2004	79.74
2005	80.31
2006	80.8
2007	81.04
2008	81.48
2009	82.12