Year current US$ 2001 533.50253682 2002 557.95952253 2003 579.86528439 2004 659.02228273 2005 647.05488852 2006 660.79144596 2007 735.41724298 2008 834.42706051 2009 786.97442242 2010 507.47437709 2011 506.56372112 2012 493.50406568 2013 454.60671892 2014 498.41297035 2015 484.89775462 2016 452.12214993 2017 459.15643754 2018 445.90022511 2019 432.46170208 2020 394.09601173 2021 489.87444129