Year	Percent
1981	0.8
1982	0.8
1983	0.8
1984	0.9
1985	0.9
1986	0.9
1987	0.7
1988	0.6
1989	0.6
1990	0.8
1992	0.8
1993	0.7
1995	0.8
1996	0.7
1997	0.7
1998	0.7
1999	0.8
2001	0.8
2002	0.9
2003	0.8
2004	0.9
2005	1
2006	1
2007	1
2008	1
2009	1
2011	1.1
2012	1.1
2013	1.1
2014	1.2
2015	1.2