Year	Percent
1979	0.1232
1990	2.4
1991	3.3
1992	4.4
1993	5.5
1994	6.4
1995	7.1
1996	7.4
1997	7.5
1998	7.4
1999	7.2
2000	6.9
2001	6.5
2002	6.1
2003	5.7
2004	5.3
2005	4.8
2006	4.4
2007	4.1
2008	3.7
2009	3.4
2010	3.2
2011	3