Year	Age
1970	1.8
1971	1.9
1972	2
1973	2.2
1974	2.3
1975	2.4
1976	2.6
1977	2.7
1978	2.9
1979	3
1980	3.2
1981	3.4
1982	3.6
1983	3.8
1984	4
1985	4.1
1986	4.3
1987	4.5
1988	4.6
1989	4.8
1990	5
1991	5.1
1992	5.3
1993	5.4
1994	5.6
1995	5.8
1996	5.9
1997	6.1
1998	6.2
1999	6.4
2000	6.5
2001	6.7
2002	6.8
2003	7
2004	7.1
2005	7.2
2006	7.4
2007	7.5
2008	7.6
2009	7.7