Year	Age
1970	6
1971	6.2
1972	6.4
1973	6.6
1974	6.8
1975	7
1976	7.2
1977	7.4
1978	7.6
1979	7.8
1980	8
1981	8.2
1982	8.4
1983	8.6
1984	8.8
1985	9
1986	9.2
1987	9.3
1988	9.5
1989	9.7
1990	9.8
1991	10
1992	10.1
1993	10.3
1994	10.5
1995	10.6
1996	10.7
1997	10.9
1998	11
1999	11.2
2000	11.3
2001	11.4
2002	11.5
2003	11.7
2004	11.8
2005	11.9
2006	12
2007	12.1
2008	12.2
2009	12.3