Year	current US$
2000	5.742962
2001	6.27754784
2002	5.47450753
2003	7.39213634
2004	9.10819047
2005	8.61113277
2006	9.05011229
2007	9.13874795
2008	8.15978667
2009	9.21408046
2010	7.59433552
2011	7.16268406
2012	8.3093871
2013	9.28487068
2014	7.2002234
2015	6.15435248
2016	4.94147078
2017	4.98966644
2018	5.36131724
2019	3.64693785
2020	3.42424029
2021	4.32541148