Year current US$ 2000 27.007497314824718 2001 28.522770544858645 2002 27.09152729211658 2003 29.400457478662755 2004 32.547074198491124 2005 38.14099561218948 2006 41.122568972293955 2007 46.92754271270747 2008 50.005786912058795 2009 47.93093374871533 2010 55.45882271592298 2011 59.96039609390895 2012 61.629734144647784 2013 64.27247101313752 2014 61.95420999912564 2015 62.06088793370406 2016 60.771500837707904 2017 57.64551641741742 2018 58.39827896515334 2019 58.006706417953225 2020 55.765028288327336 2021 63.634310834996626