Year	Percent
1990	0.06
1991	0.1
1992	0.1
1993	0.1
1994	0.1
1995	0.1
1996	0.1
1997	0.2
1998	0.2
1999	0.3
2000	0.3
2001	0.4
2002	0.4
2003	0.5
2004	0.6
2005	0.7
2006	0.7
2007	0.8
2008	0.9
2009	1
2010	1
2011	1