Year US Dollars adjusted for inflation) 1950 2972 1951 3445 1952 3585 1953 3425 1954 3858 1955 4052 1956 4327 1957 4480 1958 4632 1959 4485 1960 4965 1961 5532 1962 6045 1963 6577 1964 6858 1965 7249 1966 7723 1967 7962 1968 8374 1969 9058 1970 9327 1971 9625 1972 10350 1973 11080 1974 11620 1975 11550 1976 11840 1977 11960 1978 11960 1979 11900 1980 12060 1981 11950 1982 12030 1983 12190 1984 12350 1985 12580 1986 12950 1987 13610 1988 14250 1989 14890 1990 15400 1991 15730 1992 15830 1993 15600 1994 15920 1995 16310 1996 16660 1997 17260 1998 17980 1999 18740 2000 19540 2001 20030 2002 20320 2003 20640 2004 20970