Year US Dollars adjusted for inflation) 1960 1273.4841 1961 1276.44537 1962 1265.43269 1963 1265.65695 1964 1301.02058 1965 1332.23792 1966 1401.47669 1967 1460.57702 1968 1493.23837 1969 1562.45008 1970 1624.33188 1971 1659.86276 1972 1682.86309 1973 1600.41427 1974 1630.06137 1975 1528.91976 1976 1564.58796 1977 1544.9151 1978 1572.9093 1979 1574.80631 1980 1461.13118 1981 1379.40262 1982 1296.56604 1983 1228.98995 1984 1171.78766 1985 1144.17104 1986 1120.22467 1987 1114.47607 1988 1104.79599 1989 822.92164 1990 409.56692 1991 357.60822 1992 236.447 1993 160.25882 1994 124.59558 1995 115.79414 1996 122.85611 1997 235.45134 1998 283.43171 1999 321.90455 2000 392.49021 2001 389.54844 2002 394.73989 2003 271.02214 2004 272.85516 2005 279.79623 2006 292.03774 2007 307.39962 2008 315.87609 2009 319.65574 2010 327.42051 2011 343.6464 2012 361.23251 2013 383.07944 2014 376.58886 2015 367.47598 2016 352.64608 2017 352.28595