Year	Age
1970	2.7
1971	2.8
1972	2.9
1973	3.1
1974	3.2
1975	3.4
1976	3.5
1977	3.7
1978	3.9
1979	4
1980	4.2
1981	4.4
1982	4.5
1983	4.7
1984	4.9
1985	5.1
1986	5.2
1987	5.4
1988	5.6
1989	5.8
1990	5.9
1991	6.1
1992	6.3
1993	6.4
1994	6.6
1995	6.8
1996	7
1997	7.1
1998	7.3
1999	7.5
2000	7.6
2001	7.8
2002	7.9
2003	8.1
2004	8.3
2005	8.4
2006	8.6
2007	8.7
2008	8.9
2009	9