Year	Years
1970	0.5
1971	0.6
1972	0.6
1973	0.6
1974	0.7
1975	0.7
1976	0.8
1977	0.8
1978	0.8
1979	0.9
1980	1
1981	1
1982	1.1
1983	1.2
1984	1.2
1985	1.3
1986	1.4
1987	1.5
1988	1.6
1989	1.6
1990	1.7
1991	1.8
1992	1.9
1993	2
1994	2.1
1995	2.2
1996	2.3
1997	2.4
1998	2.6
1999	2.7
2000	2.8
2001	2.9
2002	3.1
2003	3.2
2004	3.3
2005	3.5
2006	3.6
2007	3.8
2008	3.9
2009	4.1