Year	Age
1970	1.7
1971	1.7
1972	1.8
1973	1.9
1974	2
1975	2.1
1976	2.2
1977	2.3
1978	2.4
1979	2.5
1980	2.6
1981	2.7
1982	2.9
1983	3
1984	3.1
1985	3.3
1986	3.4
1987	3.5
1988	3.6
1989	3.7
1990	3.9
1991	4
1992	4.1
1993	4.2
1994	4.3
1995	4.5
1996	4.6
1997	4.7
1998	4.8
1999	4.9
2000	5
2001	5.1
2002	5.2
2003	5.3
2004	5.4
2005	5.5
2006	5.6
2007	5.7
2008	5.8
2009	5.9