Year	Years
1970	0.5
1971	0.5
1972	0.5
1973	0.6
1974	0.6
1975	0.6
1976	0.7
1977	0.7
1978	0.7
1979	0.8
1980	0.8
1981	0.9
1982	0.9
1983	1
1984	1
1985	1.1
1986	1.1
1987	1.2
1988	1.3
1989	1.4
1990	1.4
1991	1.5
1992	1.6
1993	1.7
1994	1.8
1995	1.9
1996	2
1997	2.1
1998	2.2
1999	2.3
2000	2.4
2001	2.5
2002	2.6
2003	2.7
2004	2.8
2005	2.9
2006	3.1
2007	3.2
2008	3.3
2009	3.5