Year US Dollars adjusted for inflation) 1970 5168 1971 4979 1972 5249 1973 5022 1974 5170 1975 4871 1976 4414 1977 4717 1978 4738 1979 5263 1980 5383 1981 5281 1982 5618 1983 7076 1984 7171 1985 7499 1986 7878 1987 7852 1988 9697 1989 9985 1990 10790 1991 10710 1992 11150 1993 12000 1994 12620 1995 12020 1996 12440 1997 12950 1998 13670 1999 14060 2000 14060 2001 14320 2002 15270 2003 15820