Year US Dollars adjusted for inflation) 1970 9790 1971 8552 1972 8637 1973 7331 1974 7830 1975 9245 1976 11200 1977 11070 1978 10410 1979 10270 1980 9483 1981 10510 1982 11040 1983 11680 1984 12600 1985 13570 1986 13400 1987 12800 1988 13400 1989 13210 1990 13840 1991 14300 1992 14850 1993 15330 1994 15320 1995 15700 1996 16010 1997 16370 1998 16200 1999 15860 2000 16190 2001 17070 2002 16750 2003 16270