Year US Dollars adjusted for inflation) 1953 2235 1954 2444 1955 2647 1956 2882 1957 3178 1958 3205 1959 3263 1960 3394 1961 3526 1962 3577 1963 3759 1964 3885 1965 3951 1966 3916 1967 3851 1968 3831 1969 3925 1970 4410 1971 4498 1972 4881 1973 4854 1974 4677 1975 4452 1976 4353 1977 4274 1978 4232 1979 4026 1980 3729 1981 3761 1982 3743 1983 3913 1984 3798 1985 3619 1986 3620 1987 3966 1988 4015 1989 4244 1990 4446 1991 4419 1992 4585 1993 4743 1994 4714 1995 4682 1996 4612 1997 4561 1998 4680 1999 4541 2000 4521 2001 4580 2002 4588 2003 4584