Year	Years
1970	0.6
1971	0.7
1972	0.7
1973	0.7
1974	0.8
1975	0.8
1976	0.9
1977	0.9
1978	1
1979	1
1980	1.1
1981	1.1
1982	1.2
1983	1.2
1984	1.3
1985	1.4
1986	1.4
1987	1.5
1988	1.5
1989	1.6
1990	1.7
1991	1.8
1992	1.8
1993	1.9
1994	2
1995	2.1
1996	2.1
1997	2.2
1998	2.3
1999	2.4
2000	2.5
2001	2.6
2002	2.7
2003	2.8
2004	2.9
2005	3
2006	3.1
2007	3.2
2008	3.3
2009	3.4