Year US Dollars adjusted for inflation) 1960 238.85456 1961 245.19858 1962 256.77717 1963 250.11785 1964 252.26183 1965 257.91508 1966 255.28153 1967 273.30022 1968 276.9742 1969 277.77409 1970 273.33152 1971 272.41046 1972 273.83695 1973 270.1829 1974 287.26456 1975 290.37311 1976 309.15385 1977 304.24223 1978 311.83418 1979 316.43775 1980 311.89157 1981 317.60755 1982 339.56329 1983 332.26018 1984 318.10243 1985 336.41159 1986 353.88802 1987 343.97045 1988 354.48898 1989 352.67786 1990 341.35262 1991 362.47892 1992 353.66879 1993 356.12886 1994 351.10446 1995 361.12142 1996 389.96545 1997 403.21694 1998 420.72345 1999 439.29973 2000 434.76333 2001 450.45228 2002 456.73413 2003 478.30435 2004 485.3074 2005 511.96759 2006 527.96235 2007 541.2687 2008 563.44707 2009 562.84194 2010 575.44645 2011 595.39325 2012 615.09708 2013 631.61218 2014 639.70955 2015 645.36986 2016 663.96176 2017 688.53389