Year	Age
1970	1
1971	1
1972	1.1
1973	1.1
1974	1.2
1975	1.2
1976	1.3
1977	1.4
1978	1.4
1979	1.5
1980	1.6
1981	1.7
1982	1.8
1983	1.9
1984	2
1985	2.1
1986	2.2
1987	2.3
1988	2.3
1989	2.4
1990	2.5
1991	2.6
1992	2.7
1993	2.8
1994	2.9
1995	3
1996	3.1
1997	3.2
1998	3.3
1999	3.4
2000	3.4
2001	3.5
2002	3.6
2003	3.7
2004	3.8
2005	3.9
2006	4
2007	4.1
2008	4.1
2009	4.2