Year	Age
1970	1
1971	1.1
1972	1.2
1973	1.2
1974	1.3
1975	1.4
1976	1.5
1977	1.6
1978	1.6
1979	1.7
1980	1.8
1981	1.9
1982	2
1983	2.1
1984	2.2
1985	2.3
1986	2.4
1987	2.4
1988	2.5
1989	2.6
1990	2.7
1991	2.9
1992	3
1993	3.1
1994	3.2
1995	3.3
1996	3.4
1997	3.6
1998	3.7
1999	3.8
2000	3.9
2001	4.1
2002	4.2
2003	4.4
2004	4.5
2005	4.6
2006	4.8
2007	4.9
2008	5.1
2009	5.2