Year US Dollars adjusted for inflation) 1950 4620 1951 4936 1952 4465 1953 4265 1954 4838 1955 5320 1956 5781 1957 5717 1958 5873 1959 6291 1960 6526 1961 7106 1962 7521 1963 7918 1964 8340 1965 8700 1966 8407 1967 8420 1968 9776 1969 10890 1970 11460 1971 12250 1972 13090 1973 13980 1974 14240 1975 14490 1976 13940 1977 13490 1978 14010 1979 14350 1980 14010 1981 14580 1982 14710 1983 15010 1984 14690 1985 14710 1986 15150 1987 16190 1988 16280 1989 15910 1990 16540 1991 17160 1992 17680 1993 18000 1994 18820 1995 19660 1996 20330 1997 20510 1998 20780 1999 20960 2000 22240 2001 21600 2002 20950 2003 20720 2004 21240