Year current US$ 2000 11.64748025670598 2001 11.693907850088104 2002 12.73703638606592 2003 14.640721873157485 2004 17.187532223525597 2005 19.445684945216005 2006 22.835754756853554 2007 26.96175688669385 2008 31.658302616734108 2009 32.557523322527935 2010 33.45145097081297 2011 36.898142587587806 2012 38.615767796505274 2013 42.375482846744134 2014 44.41347472826783 2015 43.216089711849875 2016 42.721461232767744 2017 43.04570500776718 2018 42.03248405845513 2019 43.047046637010226 2020 43.958823479470446 2021 47.12790362005827