Year	Years
1970	6.4
1971	6.5
1972	6.6
1973	6.7
1974	6.9
1975	7
1976	7.1
1977	7.2
1978	7.4
1979	7.5
1980	7.6
1981	7.7
1982	7.8
1983	7.9
1984	8
1985	8.1
1986	8.2
1987	8.3
1988	8.4
1989	8.5
1990	8.6
1991	8.7
1992	8.8
1993	8.9
1994	9
1995	9.1
1996	9.2
1997	9.3
1998	9.4
1999	9.5
2000	9.6
2001	9.7
2002	9.8
2003	9.9
2004	10
2005	10.1
2006	10.2
2007	10.3
2008	10.4
2009	10.5