Year	Age
1970	1.9
1971	2
1972	2.1
1973	2.2
1974	2.3
1975	2.5
1976	2.6
1977	2.7
1978	2.9
1979	3
1980	3.2
1981	3.3
1982	3.5
1983	3.7
1984	3.8
1985	4
1986	4.1
1987	4.3
1988	4.5
1989	4.6
1990	4.8
1991	5
1992	5.2
1993	5.3
1994	5.5
1995	5.7
1996	5.9
1997	6.1
1998	6.2
1999	6.4
2000	6.6
2001	6.8
2002	7
2003	7.1
2004	7.3
2005	7.5
2006	7.7
2007	7.8
2008	8
2009	8.2