Year	Years
1970	5.7
1971	5.8
1972	5.9
1973	6
1974	6.2
1975	6.3
1976	6.4
1977	6.5
1978	6.7
1979	6.8
1980	6.9
1981	7
1982	7.1
1983	7.3
1984	7.4
1985	7.5
1986	7.6
1987	7.8
1988	7.9
1989	8
1990	8.1
1991	8.2
1992	8.4
1993	8.5
1994	8.6
1995	8.7
1996	8.8
1997	8.9
1998	9.1
1999	9.2
2000	9.3
2001	9.4
2002	9.5
2003	9.6
2004	9.7
2005	9.8
2006	9.9
2007	10
2008	10.1
2009	10.2