Year	Years
1970	0.8
1971	0.8
1972	0.9
1973	0.9
1974	0.9
1975	0.9
1976	1
1977	1
1978	1
1979	1.1
1980	1.1
1981	1.1
1982	1.2
1983	1.2
1984	1.2
1985	1.3
1986	1.4
1987	1.4
1988	1.5
1989	1.5
1990	1.6
1991	1.7
1992	1.8
1993	1.8
1994	1.9
1995	2
1996	2
1997	2.1
1998	2.2
1999	2.3
2000	2.4
2001	2.4
2002	2.5
2003	2.6
2004	2.7
2005	2.8
2006	2.8
2007	2.9
2008	3
2009	3.1