Year	current US$
2003	7.01026618
2004	8.06807342
2005	9.90921013
2006	6.69496267
2007	5.62671233
2008	4.98525303
2009	4.47094511
2010	6.21954151
2011	6.65734209
2012	6.76819014
2013	7.14522432
2014	10.62633678
2015	11.44476643
2016	10.41992703
2017	10.08173213
2018	8.01840299
2019	8.31058733
2020	8.07925104
2021	7.95266172