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