Year US Dollars adjusted for inflation) 1954 3186 1955 2622 1956 3424 1957 3489 1958 3957 1959 4202 1960 4187 1961 4581 1962 4455 1963 4615 1964 4875 1965 5231 1966 5214 1967 5307 1968 4963 1969 4871 1970 4249 1971 4022 1972 4070 1973 3802 1974 3646 1975 3273 1976 3580 1977 3383 1978 4002 1979 4227 1980 4429 1981 4245 1982 4462 1983 4572 1984 4969 1985 5058 1986 5364 1987 5272 1988 4958 1989 4063 1990 3538 1991 3408 1992 3384 1993 3412 1994 3602 1995 3783 1996 3764 1997 3891 1998 3912 1999 3892 2000 3902 2001 3905 2002 3922 2003 3742