Year current US$ 2000 12.677338699388189 2001 14.067067219327072 2002 14.143625274583789 2003 15.089012460871627 2004 17.620817812943958 2005 19.644946417279893 2006 21.144159036945396 2007 25.387676770374046 2008 25.592385613670345 2009 25.632045108432695 2010 29.83643762971978 2011 30.96014733138691 2012 31.63690064646744 2013 38.19847700558062 2014 38.891885943964944 2015 39.511702029364606 2016 40.07860662461071 2017 36.730194350294035 2018 36.76546194403983 2019 37.48146550075129 2020 38.58543475376416 2021 44.746005828155134