Year current US$ 1960 6.599345660598668 1961 4.244290079776798 1962 6.601363807482158 1963 7.08098370788649 1964 7.836372646449181 1965 3.983325782219422 1966 3.0759368563598666 1967 1.018254086731921 1968 0.773988493078465 1969 0.2912111049249909 1970 4.914613054050622 1971 3.901173575493526 1972 3.8518316607401744 1973 23.892819021621637 1974 36.28411413848042 1975 64.81991171662636 1976 61.36035750698945 1977 65.04070722697234 1978 64.89052966287676 1979 36.884337532288896 1980 31.615901206294904 1981 28.902501164933128 1982 31.61364292809203 1983 30.763828508244927 1984 36.32249893091264 1985 35.45818252149644 1986 32.46402030506951 1987 32.610087461664044 1988 27.566351688844833 1989 29.483997061998686 1990 106.00785490201545 1991 92.28364796153052 1992 62.30627454501482 1993 40.48779581814842 1994 42.88591998084677 1995 31.60616600521035 1996 33.461349460544575 1997 29.99474758200499 1998 28.84229461740933 1999 23.17692708978602 2000 19.20700046598082 2001 17.849196420349934 2002 17.59193241557736 2003 13.390409554176422 2004 19.38587353334939 2005 13.231817347206732 2006 11.27413803500467 2007 14.254533411925053 2008 20.745953166892328 2009 11.42477030566361 2010 6.866973101873194 2011 4.750333570272592 2012 19.87530228624814 2013 59.03442202029838 2014 37.00715653336611 2015 25.833318548093693 2016 24.426254358099687 2017 0.3252795002649058 2018 20.0586519903121 2019 16.156234577256328 2020 14.532713556804666 2021 72.6819681071958 2022 52.41098026241358