Year	Percent
1990	16.73
1991	16.46
1992	22.21
1993	26.05
1994	29.21
1995	35.09
1996	37.53
1997	38.98
1998	36.7
1999	37.2
2000	35.92
2001	33.62
2002	33.51
2003	32.45
2004	31.06
2005	29.63
2006	29.29
2007	30.11
2008	29.9
2009	34.88
2010	35.28