Year	Age
1970	4.1
1971	4.3
1972	4.5
1973	4.7
1974	4.8
1975	5
1976	5.2
1977	5.4
1978	5.5
1979	5.7
1980	5.9
1981	6.1
1982	6.3
1983	6.5
1984	6.6
1985	6.8
1986	7
1987	7.2
1988	7.3
1989	7.5
1990	7.7
1991	7.8
1992	8
1993	8.2
1994	8.3
1995	8.5
1996	8.6
1997	8.8
1998	9
1999	9.1
2000	9.3
2001	9.4
2002	9.6
2003	9.7
2004	9.8
2005	10
2006	10.1
2007	10.2
2008	10.4
2009	10.5