Year	Years
1990	8.5
1991	7.9
1992	7.4
1993	6.9
1994	6.5
1995	6
1996	5.7
1997	5.4
1998	5.1
1999	4.8
2000	4.6
2001	4.4
2002	4.3
2003	4.1
2004	4
2005	3.9
2006	3.7
2007	3.6
2008	3.5
2009	3.4
2010	3.3
2011	3.2
2012	3.1
2013	3