Year	Age
1970	2.2
1971	2.4
1972	2.5
1973	2.6
1974	2.7
1975	2.8
1976	2.9
1977	3.1
1978	3.2
1979	3.3
1980	3.5
1981	3.6
1982	3.7
1983	3.9
1984	4
1985	4.2
1986	4.3
1987	4.4
1988	4.5
1989	4.7
1990	4.8
1991	4.9
1992	5
1993	5.1
1994	5.2
1995	5.3
1996	5.5
1997	5.6
1998	5.7
1999	5.8
2000	5.9
2001	6
2002	6.1
2003	6.2
2004	6.3
2005	6.4
2006	6.5
2007	6.5
2008	6.6
2009	6.7