Year current US$ 2006 37801333.33333333 2007 38941481.48148148 2008 51611259.259259254 2009 51135888.88888889 2010 39885185.18518518 2011 36785185.18518518 2012 37859259.259259254 2013 43566666.666666664 2014 38777777.777777776 2015 38911111.11111111 2016 38814814.81481481 2017 31211111.11111111 2018 33570370.370370366 2019 36259259.259259254 2020 29688888.888888888 2021 31970370.37037037 2022 35462962.96296296 2023 23181481.48148148