Year	Years
1970	8.9
1971	9
1972	9.1
1973	9.2
1974	9.3
1975	9.4
1976	9.5
1977	9.6
1978	9.7
1979	9.8
1980	9.9
1981	9.9
1982	10
1983	10.1
1984	10.2
1985	10.2
1986	10.3
1987	10.4
1988	10.4
1989	10.5
1990	10.6
1991	10.7
1992	10.7
1993	10.8
1994	10.9
1995	10.9
1996	11
1997	11.1
1998	11.1
1999	11.2
2000	11.3
2001	11.3
2002	11.4
2003	11.5
2004	11.5
2005	11.6
2006	11.6
2007	11.7
2008	11.8
2009	11.8