Year US Dollars adjusted for inflation) 1951 4291 1952 4436 1953 4836 1954 4432 1955 4583 1956 4509 1957 4728 1958 4863 1959 4666 1960 5022 1961 5063 1962 5188 1963 5330 1964 5349 1965 5294 1966 5768 1967 5795 1968 5940 1969 6099 1970 6165 1971 6634 1972 6526 1973 6119 1974 6129 1975 5213 1976 5247 1977 5649 1978 6018 1979 6443 1980 6675 1981 6936 1982 5901 1983 5616 1984 5807 1985 5795 1986 5981 1987 6201 1988 6517 1989 7041 1990 7143 1991 7552 1992 8314 1993 8746 1994 9120 1995 9911 1996 10520 1997 11050 1998 11250 1999 11140 2000 11430 2001 11660 2002 11780 2003 12140 2004 12680