Year	current US$
2000	8.250324366449705
2001	7.02474036549366
2002	7.705646416269697
2003	8.589097311286318
2004	9.737922422892883
2005	11.139559612555901
2006	13.579917557707669
2007	16.614076413592866
2008	18.85275436127419
2009	18.408996928067317
2010	18.846653967306683
2011	19.11893413032347
2012	19.516626237591613
2013	21.846690253827834
2014	22.25893432292712
2015	22.418593849682296
2016	19.787574194633702
2017	17.455189424695096
2018	15.74549696483154
2019	16.60045946864966
2020	16.72316988455176
2021	17.01648148257545