Year	Percent
1984	0.01108
1990	0.8
1991	1.7
1992	3.3
1993	5.9
1994	9.8
1995	14.3
1996	18.5
1997	21.6
1998	23.4
1999	24.2
2000	24.5
2001	24.5
2002	24.3
2003	24.1
2004	23.8
2005	23.6
2006	23.5
2007	23.5
2008	23.6
2009	23
2010	23.2
2011	23.3