Year	Age
1970	3
1971	3.2
1972	3.4
1973	3.6
1974	3.8
1975	4
1976	4.2
1977	4.5
1978	4.7
1979	4.9
1980	5.2
1981	5.4
1982	5.7
1983	6
1984	6.3
1985	6.5
1986	6.8
1987	7
1988	7.3
1989	7.5
1990	7.7
1991	8
1992	8.2
1993	8.4
1994	8.7
1995	8.9
1996	9.1
1997	9.4
1998	9.6
1999	9.8
2000	10
2001	10.2
2002	10.4
2003	10.6
2004	10.8
2005	11
2006	11.1
2007	11.3
2008	11.5
2009	11.6