Year	Years
1970	0.5
1971	0.5
1972	0.6
1973	0.6
1974	0.6
1975	0.7
1976	0.7
1977	0.7
1978	0.8
1979	0.8
1980	0.9
1981	0.9
1982	0.9
1983	1
1984	1.1
1985	1.1
1986	1.2
1987	1.2
1988	1.3
1989	1.4
1990	1.4
1991	1.5
1992	1.6
1993	1.6
1994	1.7
1995	1.8
1996	1.9
1997	2
1998	2.1
1999	2.2
2000	2.2
2001	2.3
2002	2.4
2003	2.5
2004	2.7
2005	2.8
2006	2.9
2007	3
2008	3.1
2009	3.2