Year	Age
1970	2.2
1971	2.3
1972	2.4
1973	2.6
1974	2.7
1975	2.8
1976	3
1977	3.1
1978	3.3
1979	3.4
1980	3.6
1981	3.8
1982	4
1983	4.2
1984	4.4
1985	4.5
1986	4.7
1987	4.9
1988	5.1
1989	5.2
1990	5.4
1991	5.6
1992	5.7
1993	5.9
1994	6.1
1995	6.2
1996	6.4
1997	6.5
1998	6.7
1999	6.9
2000	7
2001	7.2
2002	7.3
2003	7.5
2004	7.6
2005	7.7
2006	7.9
2007	8
2008	8.1
2009	8.2