Year US Dollars adjusted for inflation) 1950 6282 1951 6119 1952 5894 1953 6665 1954 7152 1955 7789 1956 7795 1957 7618 1958 8169 1959 8216 1960 8252 1961 8085 1962 8528 1963 9308 1964 10140 1965 10730 1966 11480 1967 11300 1968 10450 1969 10510 1970 11120 1971 12810 1972 12910 1973 13850 1974 14910 1975 14680 1976 14750 1977 16260 1978 17070 1979 17720 1980 18560 1981 19150 1982 19350 1983 18680 1984 19230 1985 19640 1986 20630 1987 22200 1988 21920 1989 21700 1990 21740 1991 21510 1992 20620 1993 20590 1994 21180 1995 20980 1996 21890 1997 22840 1998 24000 1999 24720 2000 25790 2001 26310 2002 25500 2003 26350 2004 27910