Year	Years
1970	0.5
1971	0.5
1972	0.5
1973	0.6
1974	0.6
1975	0.7
1976	0.7
1977	0.8
1978	0.8
1979	0.9
1980	0.9
1981	1
1982	1.1
1983	1.2
1984	1.2
1985	1.3
1986	1.4
1987	1.5
1988	1.6
1989	1.7
1990	1.8
1991	1.9
1992	2
1993	2.1
1994	2.3
1995	2.4
1996	2.5
1997	2.6
1998	2.8
1999	2.9
2000	3
2001	3.2
2002	3.3
2003	3.5
2004	3.6
2005	3.8
2006	4
2007	4.1
2008	4.3
2009	4.5