Year US Dollars adjusted for inflation) 1970 2675 1971 2812 1972 2868 1973 2896 1974 2867 1975 3132 1976 3277 1977 3658 1978 3900 1979 3967 1980 3749 1981 4471 1982 5017 1983 5234 1984 5345 1985 6941 1986 7086 1987 7134 1988 7240 1989 7227 1990 6726 1991 6589 1992 5748 1993 4948 1994 5008 1995 4979 1996 5165 1997 5093 1998 5164 1999 5475 2000 5699 2001 5892 2002 6031 2003 6288