Year	Age
1970	1
1971	1.1
1972	1.1
1973	1.2
1974	1.3
1975	1.3
1976	1.4
1977	1.5
1978	1.6
1979	1.7
1980	1.7
1981	1.8
1982	1.9
1983	2
1984	2.1
1985	2.2
1986	2.3
1987	2.5
1988	2.6
1989	2.7
1990	2.8
1991	2.9
1992	3
1993	3.2
1994	3.3
1995	3.4
1996	3.5
1997	3.7
1998	3.8
1999	3.9
2000	4.1
2001	4.2
2002	4.3
2003	4.5
2004	4.6
2005	4.8
2006	4.9
2007	5.1
2008	5.2
2009	5.4