Year	Years
1970	5.9
1971	6
1972	6.1
1973	6.2
1974	6.3
1975	6.4
1976	6.6
1977	6.7
1978	6.8
1979	6.9
1980	7
1981	7.1
1982	7.2
1983	7.3
1984	7.4
1985	7.5
1986	7.6
1987	7.7
1988	7.8
1989	7.9
1990	8
1991	8.1
1992	8.2
1993	8.3
1994	8.4
1995	8.5
1996	8.6
1997	8.6
1998	8.7
1999	8.8
2000	8.9
2001	9
2002	9.1
2003	9.2
2004	9.3
2005	9.4
2006	9.5
2007	9.6
2008	9.7
2009	9.8