Year current US$ 2005 20760000000 2006 19137000000 2007 21662000000 2008 26446000000 2009 26331000000 2010 26318000000 2011 30302000000 2012 31566000000 2013 37984000000 2014 40028000000 2015 35648000000 2016 26505000000 2017 31993000000 2018 36791000000 2019 41415000000 2020 13771000000