Year	Years
1970	0.7
1971	0.7
1972	0.8
1973	0.8
1974	0.8
1975	0.9
1976	0.9
1977	1
1978	1
1979	1.1
1980	1.1
1981	1.2
1982	1.2
1983	1.3
1984	1.3
1985	1.4
1986	1.5
1987	1.5
1988	1.6
1989	1.7
1990	1.8
1991	1.8
1992	1.9
1993	2
1994	2.1
1995	2.2
1996	2.3
1997	2.4
1998	2.5
1999	2.6
2000	2.7
2001	2.8
2002	2.9
2003	3
2004	3.2
2005	3.3
2006	3.4
2007	3.6
2008	3.7
2009	3.8