Year Age 1970 8.5 1971 8.7 1972 8.9 1973 9.1 1974 9.4 1975 9.6 1976 9.8 1977 9.9 1978 10.1 1979 10.3 1980 10.5 1981 10.7 1982 10.8 1983 11 1984 11.1 1985 11.3 1986 11.4 1987 11.5 1988 11.6 1989 11.7 1990 11.9 1991 12 1992 12.1 1993 12.2 1994 12.3 1995 12.3 1996 12.4 1997 12.5 1998 12.6 1999 12.7 2000 12.7 2001 12.8 2002 12.9 2003 12.9 2004 13 2005 13 2006 13.1 2007 13.1 2008 13.2 2009 13.2