Year	Age
1970	5.6
1971	5.8
1972	6
1973	6.2
1974	6.5
1975	6.7
1976	6.9
1977	7.2
1978	7.4
1979	7.6
1980	7.9
1981	8.1
1982	8.4
1983	8.6
1984	8.8
1985	9
1986	9.2
1987	9.4
1988	9.6
1989	9.8
1990	10
1991	10.1
1992	10.3
1993	10.4
1994	10.6
1995	10.7
1996	10.9
1997	11
1998	11.2
1999	11.3
2000	11.4
2001	11.5
2002	11.7
2003	11.8
2004	11.9
2005	12
2006	12.1
2007	12.1
2008	12.2
2009	12.3