Year	Age
1970	1.8
1971	1.9
1972	2
1973	2.1
1974	2.2
1975	2.4
1976	2.5
1977	2.6
1978	2.8
1979	2.9
1980	3.1
1981	3.2
1982	3.4
1983	3.6
1984	3.7
1985	3.9
1986	4
1987	4.2
1988	4.4
1989	4.5
1990	4.7
1991	4.9
1992	5
1993	5.2
1994	5.4
1995	5.6
1996	5.7
1997	5.9
1998	6.1
1999	6.3
2000	6.5
2001	6.6
2002	6.8
2003	7
2004	7.1
2005	7.3
2006	7.5
2007	7.6
2008	7.8
2009	8