Year	Percent
1990	32
1991	32.2
1992	32.4
1993	32.7
1994	33.4
1995	33.5
1996	33.6
1997	29.4
1998	28.1
1999	34.6
2000	34.6
2001	34.6
2006	34.12
2007	36.65
2008	38.14
2009	41.96