Year current US$ 2000 0.44471251 2001 0.50506042 2002 0.62937968 2003 0.89461603 2004 1.17614271 2005 1.41518547 2006 1.72428394 2007 2.28157949 2008 2.98401268 2009 3.09084723 2010 1.83410847 2011 2.95795631 2012 3.6951311 2013 6.65164695 2014 6.4466797 2015 5.81084776 2016 7.97524724 2017 7.94162438 2018 5.11742339 2019 4.57205282 2020 8.17367385 2021 8.75908325