Year	Age
1970	3.2
1971	3.4
1972	3.6
1973	3.7
1974	3.9
1975	4.1
1976	4.3
1977	4.5
1978	4.7
1979	4.9
1980	5.1
1981	5.3
1982	5.5
1983	5.7
1984	6
1985	6.2
1986	6.4
1987	6.6
1988	6.8
1989	7
1990	7.2
1991	7.4
1992	7.6
1993	7.8
1994	7.9
1995	8.1
1996	8.3
1997	8.5
1998	8.7
1999	8.9
2000	9.1
2001	9.3
2002	9.4
2003	9.6
2004	9.8
2005	9.9
2006	10.1
2007	10.2
2008	10.4
2009	10.6