Year	Age
1970	1.8
1971	1.9
1972	2.1
1973	2.2
1974	2.3
1975	2.4
1976	2.5
1977	2.6
1978	2.7
1979	2.9
1980	3
1981	3.1
1982	3.2
1983	3.3
1984	3.4
1985	3.6
1986	3.7
1987	3.8
1988	3.9
1989	4
1990	4.2
1991	4.3
1992	4.4
1993	4.5
1994	4.7
1995	4.8
1996	4.9
1997	5
1998	5.2
1999	5.3
2000	5.4
2001	5.6
2002	5.7
2003	5.8
2004	6
2005	6.1
2006	6.2
2007	6.4
2008	6.5
2009	6.6