Year	Years
1970	5.2
1971	5.3
1972	5.4
1973	5.6
1974	5.7
1975	5.8
1976	6
1977	6.1
1978	6.2
1979	6.4
1980	6.5
1981	6.6
1982	6.7
1983	6.9
1984	7
1985	7.1
1986	7.3
1987	7.4
1988	7.5
1989	7.6
1990	7.8
1991	7.9
1992	8
1993	8.1
1994	8.2
1995	8.4
1996	8.5
1997	8.6
1998	8.7
1999	8.8
2000	9
2001	9.1
2002	9.2
2003	9.3
2004	9.4
2005	9.5
2006	9.7
2007	9.8
2008	9.9
2009	10