Year	Percent
1990	0.3
1991	0.36
1992	0.43
1993	0.5
1994	0.57
1995	0.65
1996	0.71
1997	0.76
1998	0.79
1999	0.8
2000	0.78
2001	0.74
2002	0.69
2003	0.63
2004	0.57
2005	0.51
2006	0.46
2007	0.43
2008	0.42
2009	0.4
2010	0.37
2011	0.34