Year	Age
1970	5.3
1971	5.5
1972	5.7
1973	5.9
1974	6.1
1975	6.2
1976	6.4
1977	6.6
1978	6.8
1979	6.9
1980	7.1
1981	7.2
1982	7.4
1983	7.5
1984	7.7
1985	7.8
1986	7.9
1987	8.1
1988	8.2
1989	8.3
1990	8.4
1991	8.5
1992	8.6
1993	8.7
1994	8.8
1995	8.9
1996	9
1997	9.1
1998	9.2
1999	9.3
2000	9.4
2001	9.4
2002	9.5
2003	9.6
2004	9.7
2005	9.8
2006	9.8
2007	9.9
2008	10
2009	10