Year Age 1970 1.3 1971 1.4 1972 1.5 1973 1.6 1974 1.6 1975 1.7 1976 1.8 1977 1.9 1978 2 1979 2.1 1980 2.2 1981 2.3 1982 2.4 1983 2.5 1984 2.6 1985 2.7 1986 2.8 1987 2.9 1988 3 1989 3.1 1990 3.2 1991 3.4 1992 3.5 1993 3.6 1994 3.7 1995 3.9 1996 4 1997 4.1 1998 4.2 1999 4.4 2000 4.5 2001 4.6 2002 4.8 2003 4.9 2004 5 2005 5.2 2006 5.3 2007 5.4 2008 5.6 2009 5.7