Year	current US$
2000	3.84930732
2001	3.0396859
2002	4.07182312
2003	4.3926905
2004	3.38260808
2005	4.24832817
2006	4.04956834
2007	3.39739568
2008	7.3762032
2009	6.4362363
2010	7.53638249
2011	8.57453327
2012	5.21028249
2013	7.1866197
2014	8.10350029
2015	10.10650548
2016	8.48989707
2017	8.59882968
2018	9.03685326
2019	9.78297574
2020	9.48228383
2021	8.5594809