Year	current US$
2000	4.173984960396876
2001	4.47883477948045
2002	4.573596571217495
2003	5.2615308411188515
2004	5.573366640805993
2005	6.229610127451562
2006	6.552440487222512
2007	8.079593720932813
2008	8.300682419032684
2009	8.782488772352854
2010	8.460057944524843
2011	7.709847048999519
2012	8.244022134200314
2013	7.444767793730528
2014	8.046852871636453
2015	6.91077924065803
2016	7.628874926633337
2017	7.000923689826581
2018	6.551562039494373
2019	6.595732115332746
2020	8.176675874229753
2021	8.145537189415156