Year US Dollars adjusted for inflation) 1970 11830 1971 11680 1972 11540 1973 10780 1974 17750 1975 18690 1976 19710 1977 21460 1978 19650 1979 19000 1980 18490 1981 17410 1982 17760 1983 17620 1984 17160 1985 15660 1986 15590 1987 15570 1988 16440 1989 16660 1990 17190 1991 16360 1992 17100 1993 19600 1994 15800 1995 16910 1996 16870 1997 16890 1998 17050 1999 18050 2000 18650 2001 19090 2002 18880 2003 19560