Year US Dollars adjusted for inflation) 1950 10980 1951 11770 1952 11500 1953 11740 1954 12370 1955 13060 1956 13810 1957 14080 1958 13310 1959 14260 1960 15250 1961 16210 1962 16690 1963 17130 1964 17830 1965 17950 1966 18140 1967 18510 1968 18960 1969 19770 1970 21080 1971 21840 1972 22480 1973 23070 1974 23230 1975 21140 1976 21040 1977 21670 1978 22120 1979 22890 1980 24040 1981 24230 1982 23770 1983 23820 1984 24390 1985 24940 1986 25240 1987 25370 1988 25900 1989 26720 1990 27450 1991 26980 1992 26750 1993 26570 1994 26820 1995 26840 1996 26790 1997 27090 1998 27850 1999 27970 2000 28830 2001 29020 2002 28990 2003 28790 2004 29280