Year	current US$
2000	6.8263686
2001	7.45101751
2002	6.68356613
2003	7.70653304
2004	9.4431968
2005	11.89931637
2006	15.27774341
2007	12.83669097
2008	12.78512463
2009	8.83670254
2010	8.6457492
2011	7.93590918
2012	8.83816276
2013	9.85797095
2014	9.1275437
2015	7.09835658
2016	6.78355447
2017	7.62107032
2018	7.23081082
2019	6.21097008
2020	4.90352058
2021	5.33275065