Year	Age
1970	4.9
1971	5.1
1972	5.2
1973	5.4
1974	5.5
1975	5.7
1976	5.9
1977	6
1978	6.2
1979	6.3
1980	6.5
1981	6.6
1982	6.8
1983	6.9
1984	7.1
1985	7.3
1986	7.4
1987	7.5
1988	7.7
1989	7.8
1990	8
1991	8.1
1992	8.3
1993	8.4
1994	8.5
1995	8.7
1996	8.8
1997	9
1998	9.1
1999	9.2
2000	9.3
2001	9.5
2002	9.6
2003	9.7
2004	9.8
2005	9.9
2006	10.1
2007	10.2
2008	10.3
2009	10.4