Year	Percent
1990	0.3
1991	0.4
1992	0.7
1993	0.9
1994	1.3
1995	1.7
1996	2
1997	2.2
1998	2.3
1999	2.3
2000	2.3
2001	2.3
2002	2.2
2003	2.1
2004	2.1
2005	2
2006	1.9
2007	1.9
2008	1.8
2009	1.6
2010	1.5
2011	1.5