Year US Dollars adjusted for inflation) 1970 64640 1971 64340 1972 63450 1973 54960 1974 45990 1975 38650 1976 39620 1977 37460 1978 36600 1979 39800 1980 29580 1981 25130 1982 23300 1983 21290 1984 20710 1985 19950 1986 19710 1987 19880 1988 19590 1989 22450 1990 16420 1991 21860 1992 25300 1993 31000 1994 30140 1995 30570 1996 30510 1997 28780 1998 28030 1999 25350 2000 25140 2001 24520 2002 23140 2003 26100