Year	Percent
1990	0.06
1991	0.06
1992	0.06
1993	0.1
1994	0.1
1995	0.1
1996	0.1
1997	0.2
1998	0.2
1999	0.2
2000	0.3
2001	0.4
2002	0.4
2003	0.5
2004	0.5
2005	0.6
2006	0.6
2007	0.6
2008	0.6
2009	0.7
2010	0.7
2011	0.7