Year Age 1970 6.6 1971 6.7 1972 6.9 1973 7 1974 7.2 1975 7.4 1976 7.5 1977 7.7 1978 7.8 1979 8 1980 8.1 1981 8.3 1982 8.4 1983 8.5 1984 8.7 1985 8.8 1986 8.9 1987 9.1 1988 9.2 1989 9.3 1990 9.4 1991 9.5 1992 9.7 1993 9.8 1994 9.9 1995 10 1996 10.1 1997 10.2 1998 10.3 1999 10.5 2000 10.6 2001 10.7 2002 10.8 2003 10.9 2004 11 2005 11.1 2006 11.2 2007 11.3 2008 11.4 2009 11.4