Year	Years
1970	5.3
1971	5.4
1972	5.6
1973	5.7
1974	5.8
1975	6
1976	6.1
1977	6.2
1978	6.3
1979	6.5
1980	6.6
1981	6.7
1982	6.8
1983	6.9
1984	7
1985	7.2
1986	7.3
1987	7.4
1988	7.5
1989	7.6
1990	7.7
1991	7.8
1992	7.9
1993	8
1994	8.1
1995	8.2
1996	8.3
1997	8.4
1998	8.5
1999	8.6
2000	8.7
2001	8.8
2002	8.9
2003	9
2004	9.1
2005	9.2
2006	9.3
2007	9.4
2008	9.5
2009	9.6