Year	Years
1970	0.5
1971	0.5
1972	0.5
1973	0.6
1974	0.6
1975	0.6
1976	0.6
1977	0.7
1978	0.7
1979	0.7
1980	0.7
1981	0.8
1982	0.8
1983	0.8
1984	0.9
1985	0.9
1986	1
1987	1
1988	1.1
1989	1.1
1990	1.1
1991	1.2
1992	1.2
1993	1.3
1994	1.3
1995	1.4
1996	1.5
1997	1.5
1998	1.6
1999	1.6
2000	1.7
2001	1.7
2002	1.8
2003	1.9
2004	1.9
2005	2
2006	2.1
2007	2.1
2008	2.2
2009	2.3