Year	Percent
1979	0.01591
1990	3.9
1991	4.5
1992	5.1
1993	5.5
1994	5.8
1995	5.9
1996	5.9
1997	5.8
1998	5.7
1999	5.4
2000	5.2
2001	5
2002	4.7
2003	4.5
2004	4.2
2005	4
2006	3.8
2007	3.6
2008	3.5
2009	1.6
2010	1.4
2011	1.3