Year US Dollars adjusted for inflation) 1950 10030 1951 9500 1952 9423 1953 9399 1954 10200 1955 10370 1956 10320 1957 10610 1958 10560 1959 10750 1960 12100 1961 12510 1962 12500 1963 12990 1964 13380 1965 14010 1966 14670 1967 13780 1968 13600 1969 14760 1970 14360 1971 14630 1972 15060 1973 15910 1974 16620 1975 16110 1976 16170 1977 15540 1978 15460 1979 15480 1980 15580 1981 16010 1982 16010 1983 16650 1984 17310 1985 17190 1986 17480 1987 17500 1988 17660 1989 17370 1990 17170 1991 16860 1992 16720 1993 17500 1994 18140 1995 18590 1996 18980 1997 19360 1998 19400 1999 20180 2000 20420 2001 20980 2002 21710 2003 22200 2004 22800