Year current US$ 2000 0.5224013178576881 2001 0.6112405251367385 2002 0.661585641231008 2003 1.0203141162323897 2004 2.0729752501220893 2005 2.000171545232354 2006 1.6521725931553686 2007 2.316879790271889 2008 2.6190708557799 2009 2.2927218589140916 2010 2.5838320196328612 2011 2.8301592077618594 2012 2.707972420515211 2013 2.757680930720801 2014 2.6045191964795613 2015 2.144531851502029 2016 2.094376579035078 2017 2.1601244881976487 2018 2.0142289237885813 2019 2.0429139697579264 2020 1.9312698882746895 2021 4.2176641353510105