Year	Percent
1979	0.01
1990	3.6
1991	3.8
1992	3.9
1993	3.9
1994	3.8
1995	3.7
1996	3.6
1997	3.5
1998	3.3
1999	3.2
2000	3.2
2001	3.1
2002	3
2003	3
2004	3
2005	3
2006	3
2007	3.1
2008	3.1
2009	2.9
2010	2.8
2011	2.8