Year	Years
1970	0.7
1971	0.7
1972	0.8
1973	0.8
1974	0.8
1975	0.9
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	1.3
1986	1.4
1987	1.4
1988	1.4
1989	1.5
1990	1.5
1991	1.6
1992	1.6
1993	1.7
1994	1.8
1995	1.8
1996	1.9
1997	1.9
1998	2
1999	2
2000	2.1
2001	2.1
2002	2.2
2003	2.3
2004	2.3
2005	2.4
2006	2.4
2007	2.5
2008	2.6
2009	2.6