Year	current US$
2000	2.26174906
2001	2.23309849
2002	2.23901243
2003	2.26696033
2004	2.29745706
2005	2.33557751
2006	3.62704061
2007	4.71533646
2008	5.45083721
2009	7.20605046
2010	7.92265558
2011	8.00247775
2012	9.85153641
2013	9.71769827
2014	12.88863123
2015	13.29391303
2016	13.51282701
2017	9.73136511
2018	9.6940594
2019	11.34381072
2020	10.70918397
2021	10.90109177