Year	Percent
1990	14.82
1991	16.74
1992	18.43
1993	19.55
1994	24.81
1995	27.15
1996	28.47
1997	30.83
1998	31.62
1999	30.25
2000	29.67
2001	31.41
2002	31.81
2003	30.76
2004	29.85
2005	31.03
2006	30.43
2007	29.74
2008	30.14
2009	30.72
2010	32.02