Year current US$ 2000 10.836317554626396 2001 10.40176843177266 2002 10.60497284664233 2003 15.559356445741724 2004 17.057640233362502 2005 19.092404840665576 2006 22.142974516825348 2007 24.440064728528963 2008 27.107546742642054 2009 24.650199964131186 2010 26.685064836907955 2011 28.611204674237904 2012 29.11088067612681 2013 31.824435597847415 2014 31.396117973884916 2015 29.001997026591134 2016 26.273025870918875 2017 25.134699715855813 2018 23.232948250858147 2019 23.002713557949036 2020 22.505460064673148 2021 25.322538287650477