Year US Dollars adjusted for inflation) 1970 5725 1971 5872 1972 6419 1973 6880 1974 7054 1975 7235 1976 7501 1977 7987 1978 7886 1979 8523 1980 8503 1981 8779 1982 9081 1983 9198 1984 9475 1985 9554 1986 9769 1987 10160 1988 10330 1989 10330 1990 10090 1991 9018 1992 9035 1993 9541 1994 9408 1995 9534 1996 9595 1997 10000 1998 10400 1999 10820 2000 11380 2001 11950 2002 12520 2003 13020 2004 13640