Year US Dollars 2009 444.02018 2010 297.08057 2011 325.61697 2012 313.61746 2013 312.71364 2014 319.61567 2015 244.83334 2016 208.16773 2017 219.07836 2018 192.03877 2019 192.74093 2020 303.88244 2021 253.32608