Year	Years
1970	0.7
1971	0.7
1972	0.7
1973	0.8
1974	0.8
1975	0.9
1976	0.9
1977	1
1978	1
1979	1.1
1980	1.2
1981	1.2
1982	1.3
1983	1.4
1984	1.4
1985	1.5
1986	1.6
1987	1.6
1988	1.7
1989	1.8
1990	1.9
1991	2
1992	2.1
1993	2.1
1994	2.2
1995	2.3
1996	2.4
1997	2.5
1998	2.6
1999	2.7
2000	2.8
2001	2.9
2002	3.1
2003	3.2
2004	3.3
2005	3.4
2006	3.5
2007	3.7
2008	3.8
2009	3.9