Year	Percent
1990	13.8
1991	13.8
1992	13.8
1993	13.8
1994	13.8
1995	15.9
1996	16.7
1997	17.2
1998	18.3
1999	18.9
2000	18.4
2001	20.2
2004	26.27
2005	21.04
2006	21.32
2007	21.43
2008	21.83
2009	22.45