Year current US$ 2000 14.87743694 2001 14.64844474 2002 16.04762353 2003 20.17915515 2004 21.93851058 2005 23.25929389 2006 26.48448527 2007 28.77688134 2008 30.69551324 2009 30.96524295 2010 40.12282443 2011 39.43065125 2012 41.14995279 2013 43.96442048 2014 46.62886482 2015 38.67990633 2016 41.41608481 2017 44.98750495 2018 46.68150375 2019 46.54638289 2020 40.8951711 2021 45.90068947