Year current US$ 2000 0.8648173 2001 0.94692675 2002 0.65916776 2003 0.8178893 2004 1.71819008 2005 1.45830566 2006 2.76035606 2007 3.93147477 2008 6.18278732 2009 5.16081289 2010 5.65086844 2011 5.56719677 2012 5.66920318 2013 4.54626881 2014 5.13294196 2015 4.29761759 2016 4.99243189 2017 8.66631217 2018 8.61945801 2019 8.95723634 2020 9.88554346 2021 7.49517467