Year current US$ 2000 9.04719516 2001 10.79977993 2002 10.89492045 2003 13.31437928 2004 12.89117402 2005 12.56240749 2006 13.40347204 2007 20.70431751 2008 13.58624864 2009 13.21871086 2010 6.7835661 2011 10.32289777 2012 6.57286773 2013 5.94718413 2014 27.60935398 2015 8.43504286 2016 4.92757879 2017 4.55262789 2018 7.16109655 2019 8.75027674 2020 8.14480509 2021 8.91192568