Year US Dollars adjusted for inflation) 1960 3898 1961 3530 1962 2626 1963 3284 1964 3778 1965 4086 1966 3685 1967 3836 1968 4017 1969 4100 1970 4280 1971 3830 1972 4621 1973 4426 1974 4044 1975 3988 1976 4343 1977 4277 1978 4437 1979 5281 1980 5056 1981 4912 1982 5163 1983 5278 1984 5461 1985 5457 1986 5743 1987 5934 1988 5573 1989 5578 1990 5570 1991 5537 1992 5617 1993 5432 1994 5228 1995 5324 1996 5513 1997 5457 1998 5508 1999 5611 2000 5753 2001 5726 2002 5723 2003 5993