Year Age 1970 7.1 1971 7.4 1972 7.6 1973 7.8 1974 8.1 1975 8.3 1976 8.6 1977 8.8 1978 9 1979 9.2 1980 9.5 1981 9.7 1982 9.9 1983 10.1 1984 10.3 1985 10.5 1986 10.7 1987 10.8 1988 11 1989 11.1 1990 11.3 1991 11.4 1992 11.6 1993 11.7 1994 11.8 1995 11.9 1996 12.1 1997 12.2 1998 12.3 1999 12.4 2000 12.5 2001 12.6 2002 12.7 2003 12.8 2004 12.9 2005 12.9 2006 13 2007 13.1 2008 13.2 2009 13.2