Year	Age
1970	6.8
1971	7.1
1972	7.4
1973	7.6
1974	7.9
1975	8.1
1976	8.4
1977	8.6
1978	8.9
1979	9.1
1980	9.4
1981	9.6
1982	9.8
1983	10.1
1984	10.3
1985	10.5
1986	10.7
1987	10.9
1988	11.1
1989	11.3
1990	11.5
1991	11.7
1992	11.9
1993	12.1
1994	12.3
1995	12.4
1996	12.6
1997	12.7
1998	12.9
1999	13
2000	13.2
2001	13.3
2002	13.4
2003	13.5
2004	13.6
2005	13.7
2006	13.9
2007	14
2008	14
2009	14.1