Year	Years
1986	14.3
1987	13.4
1988	12.5
1989	11.7
1990	10.9
1991	10.2
1992	9.5
1993	8.9
1994	8.3
1995	7.8
1996	7.3
1997	6.8
1998	6.3
1999	5.9
2000	5.5
2001	5.2
2002	4.9
2003	4.6
2004	4.4
2005	4.2
2006	4
2007	3.9
2008	3.7
2009	3.6
2010	3.4
2011	3.3
2012	3.2
2013	3.1