Year	current US$
2000	8.999823462536813
2001	8.520620129678882
2002	9.26240643949542
2003	10.339138708777826
2004	11.565327999479457
2005	12.365479348666927
2006	14.073359491665745
2007	16.463496674754115
2008	18.34865584081333
2009	17.49934914955184
2010	17.9139517100236
2011	19.35897854429323
2012	19.49513736138356
2013	21.93639393014595
2014	21.304828279571502
2015	20.57489862832097
2016	19.911991760199083
2017	19.263318294455935
2018	18.416097269944533
2019	18.666300937796308
2020	18.330233866851305
2021	19.542919649312886