Year	current US$
2000	6.15358108
2001	6.06748254
2002	5.9879881
2003	5.90858532
2004	5.82938271
2005	5.75036515
2006	8.50666852
2007	8.60094893
2008	8.52239703
2009	7.88004152
2010	8.00012149
2011	8.04561077
2012	8.5531708
2013	8.35724947
2014	8.8719183
2015	9.16136059
2016	9.3035912
2017	9.92670242
2018	10.04800308
2019	9.52754185
2020	7.47426435
2021	9.02896637