Year current US$ 2000 0.76758833 2001 0.61720009 2002 1.08302597 2003 0.90245663 2004 1.39828064 2005 2.02846094 2006 2.04922539 2007 2.5111732 2008 3.29920134 2009 2.89213937 2010 3.96235175 2011 7.01578963 2012 4.42990879 2013 4.13776092 2014 6.55419263 2015 4.98698247 2016 5.03691023 2017 4.7692846 2018 8.24541248 2019 7.33070097 2020 7.01362837 2021 10.80995866