Year	Percent
1990	22.07
1991	20.25
1992	24.53
1993	29.03
1994	32.85
1995	32.63
1996	36.11
1997	33.27
1998	32.5
1999	34.26
2000	33.8
2001	31.88
2002	32.13
2003	31.96
2004	29.04
2005	29.26
2006	30.92
2007	28
2008	29.68
2009	25.58
2010	34.18