Year US Dollars adjusted for inflation) 1970 3138 1971 3291 1972 3460 1973 3946 1974 3917 1975 3916 1976 3987 1977 4027 1978 4108 1979 4626 1980 4464 1981 4324 1982 4312 1983 3999 1984 4323 1985 4482 1986 4059 1987 4124 1988 3931 1989 4071 1990 5169 1991 5194 1992 4883 1993 4672 1994 4750 1995 4753 1996 5017 1997 4777 1998 4763 1999 4678 2000 4572 2001 4656 2002 4891 2003 4919