Year Age 1970 0.5 1971 0.5 1972 0.6 1973 0.6 1974 0.6 1975 0.7 1976 0.7 1977 0.8 1978 0.8 1979 0.8 1980 0.9 1981 0.9 1982 1 1983 1 1984 1.1 1985 1.2 1986 1.2 1987 1.3 1988 1.3 1989 1.4 1990 1.4 1991 1.5 1992 1.6 1993 1.6 1994 1.7 1995 1.8 1996 1.8 1997 1.9 1998 2 1999 2 2000 2.1 2001 2.2 2002 2.2 2003 2.3 2004 2.4 2005 2.4 2006 2.5 2007 2.6 2008 2.6 2009 2.7