Year	Years
1970	8.4
1971	8.5
1972	8.6
1973	8.7
1974	8.8
1975	8.9
1976	9
1977	9.1
1978	9.2
1979	9.3
1980	9.4
1981	9.5
1982	9.6
1983	9.6
1984	9.7
1985	9.8
1986	9.9
1987	10
1988	10.1
1989	10.1
1990	10.2
1991	10.3
1992	10.4
1993	10.4
1994	10.5
1995	10.6
1996	10.7
1997	10.7
1998	10.8
1999	10.9
2000	10.9
2001	11
2002	11.1
2003	11.1
2004	11.2
2005	11.3
2006	11.3
2007	11.4
2008	11.4
2009	11.5