Year	Percent
1979	0.155
1990	1.3
1991	1.6
1992	2.3
1993	3.3
1994	3.6
1995	3.6
1996	3.4
1997	3.3
1998	3.1
1999	2.9
2000	2.8
2001	2.6
2002	2.5
2003	2.3
2004	2.2
2005	2.1
2006	2.1
2007	2
2008	2
2009	1.9
2010	1.9
2011	1.8