Year	Age
1970	6.4
1971	6.6
1972	6.8
1973	7
1974	7.2
1975	7.4
1976	7.6
1977	7.8
1978	8
1979	8.2
1980	8.4
1981	8.6
1982	8.8
1983	9
1984	9.1
1985	9.3
1986	9.5
1987	9.6
1988	9.8
1989	10
1990	10.1
1991	10.3
1992	10.4
1993	10.6
1994	10.7
1995	10.9
1996	11
1997	11.1
1998	11.3
1999	11.4
2000	11.5
2001	11.7
2002	11.8
2003	11.9
2004	12
2005	12.1
2006	12.2
2007	12.4
2008	12.5
2009	12.6