Year	Percent
1980	0.01532
1990	7.2
1991	8.8
1992	10.5
1993	11.9
1994	13.1
1995	13.9
1996	14.5
1997	14.7
1998	14.7
1999	14.5
2000	14.2
2001	13.8
2002	13.4
2003	13
2004	12.5
2005	12.1
2006	11.8
2007	11.4
2008	11.2
2009	10.9
2010	10.4
2011	10