Year	Percent
1990	13.36
1991	12.61
1992	13.11
1993	30.56
1994	32.6
1995	31.94
1996	32.63
1997	33.73
1998	33.85
1999	33.49
2000	33.49
2001	34.07
2002	32.73
2003	33.07
2004	32.1
2005	26.81
2006	27.06
2007	26.25
2008	26.2
2009	26.16
2010	25