Year	Years
1970	7
1971	7.1
1972	7.2
1973	7.3
1974	7.4
1975	7.6
1976	7.7
1977	7.8
1978	7.9
1979	8
1980	8.1
1981	8.3
1982	8.4
1983	8.5
1984	8.6
1985	8.7
1986	8.9
1987	9
1988	9.1
1989	9.2
1990	9.3
1991	9.4
1992	9.5
1993	9.6
1994	9.7
1995	9.8
1996	9.9
1997	10
1998	10.1
1999	10.2
2000	10.3
2001	10.4
2002	10.5
2003	10.6
2004	10.7
2005	10.8
2006	10.9
2007	10.9
2008	11
2009	11.1