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