Year	Age
1970	2.1
1971	2.2
1972	2.4
1973	2.5
1974	2.6
1975	2.8
1976	2.9
1977	3.1
1978	3.2
1979	3.4
1980	3.5
1981	3.7
1982	3.9
1983	4.1
1984	4.3
1985	4.5
1986	4.6
1987	4.8
1988	5
1989	5.2
1990	5.4
1991	5.6
1992	5.8
1993	6
1994	6.2
1995	6.4
1996	6.6
1997	6.8
1998	7
1999	7.2
2000	7.4
2001	7.6
2002	7.8
2003	8
2004	8.2
2005	8.3
2006	8.5
2007	8.7
2008	8.9
2009	9.1