Year Age 1970 7.3 1971 7.5 1972 7.7 1973 7.9 1974 8.1 1975 8.3 1976 8.4 1977 8.6 1978 8.8 1979 9 1980 9.1 1981 9.3 1982 9.4 1983 9.6 1984 9.7 1985 9.9 1986 10 1987 10.1 1988 10.2 1989 10.4 1990 10.5 1991 10.6 1992 10.7 1993 10.8 1994 10.9 1995 11 1996 11.1 1997 11.2 1998 11.3 1999 11.4 2000 11.5 2001 11.6 2002 11.7 2003 11.8 2004 11.9 2005 11.9 2006 12 2007 12.1 2008 12.2 2009 12.2