Year US Dollars adjusted for inflation) 1952 334.2 1953 351 1954 349.4 1955 362.7 1956 393.7 1957 402.2 1958 438 1959 441.1 1960 444.9 1961 377.7 1962 371.7 1963 390.5 1964 425.7 1965 462.3 1966 484.9 1967 457.5 1968 432.3 1969 466.7 1970 500 1971 533.9 1972 536.3 1973 561.9 1974 561.5 1975 588.9 1976 591.7 1977 616 1978 667.8 1979 723.6 1980 751 1981 802.7 1982 888.5 1983 944.5 1984 1061 1985 1135 1986 1293 1987 1414 1988 1489 1989 1497 1990 1678 1991 1798 1992 1983 1993 2131 1994 2453 1995 2702 1996 2925 1997 3229 1998 3475 1999 3691 2000 4002 2001 4281 2002 4630 2003 4970 2004 5333