Year Age 1970 6.1 1971 6.4 1972 6.6 1973 6.8 1974 7 1975 7.2 1976 7.4 1977 7.6 1978 7.9 1979 8.1 1980 8.3 1981 8.5 1982 8.7 1983 8.9 1984 9.1 1985 9.3 1986 9.5 1987 9.7 1988 9.9 1989 10.1 1990 10.2 1991 10.4 1992 10.6 1993 10.8 1994 10.9 1995 11.1 1996 11.2 1997 11.4 1998 11.5 1999 11.7 2000 11.8 2001 12 2002 12.1 2003 12.2 2004 12.3 2005 12.5 2006 12.6 2007 12.7 2008 12.8 2009 12.9