Year current US$ 1960 1.6417520969705577 1961 0.9629281719405423 1962 1.2581662176788129 1963 1.8095112824536388 1964 0.8998299932349132 1965 0.704495679121524 1966 0.6751237386148513 1967 0.503930231165389 1968 0.5955281110912867 1969 1.0739144287390838 1970 0.8440810053354678 1971 1.46301518589653 1972 1.5529587893487726 1973 2.4169085357219537 1974 2.241870812986496 1975 1.8013281927508207 1976 2.1036555853736494 1977 2.9101940018711283 1978 6.712007607976529 1979 10.424480461479067 1980 8.80093008375621 1981 7.636741185392519 1982 8.095252322322812 1983 7.95471782996981 1984 6.711589870546598 1985 8.44580736200829 1986 9.917401873750425 1987 8.221133615211226 1988 10.283195069947956 1989 3.7812662506941166 1990 3.854406994476822 1991 4.291241890174326 1992 2.7722129613135404 1993 2.477487570069179 1994 4.184272334147426 1995 3.7418213845490778 1996 1.1380968199161445 1997 1.3881546679799093 1998 1.6270486858920143 1999 1.799446251280877 2000 2.3198038827958825 2001 2.731076244185841 2002 2.560873704353378 2003 2.664291535368812 2004 2.607816846126339 2005 3.034711517935002 2006 3.0300527466189986 2007 4.04350053142335 2008 10.970565682869484 2009 7.262142615604435 2010 7.18592657890816 2011 7.630357656752504 2012 10.04675893362727 2013 77.71470068862482 2014 27.107772202945245 2015 22.696394171317355 2016 29.612458556842164 2017 29.49682350450381 2018 32.50369328919235 2019 38.531897086579896 2020 53.72684745989242 2021 28.003972382989513 2022 18.518879272013375