Year current international $ 2000 16.30778541984102 2001 17.426407745486348 2002 17.380159289025855 2003 19.820575219929005 2004 19.578083574465108 2005 20.149908692882796 2006 20.074506274178024 2007 21.916593003133265 2008 19.874938752451477 2009 22.651133995817272 2010 20.870344844516953 2011 18.56496749640172 2012 19.850353511400062 2013 17.655933032629104 2014 19.407010703994004 2015 17.60079770095832 2016 22.367216016601535 2017 20.511680757844704 2018 19.715443067355626 2019 19.73775675624358 2020 24.97552031731448 2021 23.82407370937667