Year US Dollars adjusted for inflation) 1970 8415 1971 8855 1972 9379 1973 9417 1974 8701 1975 8904 1976 9785 1977 10250 1978 10900 1979 10770 1980 10720 1981 10420 1982 10160 1983 10860 1984 10990 1985 11870 1986 12360 1987 13130 1988 13950 1989 14680 1990 15120 1991 15430 1992 15650 1993 16150 1994 16690 1995 16420 1996 16780 1997 17860 1998 18570 1999 19340 2000 21210 2001 21010 2002 21490 2003 22230