Year	current US$
2000	4.06797857
2001	4.48464835
2002	3.5587916
2003	4.31204734
2004	3.64999202
2005	4.72276907
2006	4.22306841
2007	4.48776899
2008	4.97258651
2009	11.84794063
2010	7.17000096
2011	5.12546815
2012	6.83878888
2013	12.93796531
2014	13.56874212
2015	18.36205103
2016	17.66305954
2017	21.67594866
2018	22.19453928
2019	25.04767076
2020	20.05841067
2021	18.05427327