Year	current US$
2000	6.780127760209459
2001	6.618963788803482
2002	7.355520785194258
2003	8.328098064844655
2004	9.56871665824017
2005	10.479303294072677
2006	11.918523917070756
2007	14.409050798056509
2008	16.752231857824306
2009	16.633822777012814
2010	17.5805532135093
2011	19.05743943864618
2012	19.906538235326956
2013	22.527545434597517
2014	23.973339955781956
2015	24.902516432219674
2016	24.108150695612867
2017	23.414343243286122
2018	22.664122398375284
2019	23.575089438305326
2020	24.17520574805478
2021	24.601988909669302