Year	current US$
2000	3.74351941
2001	3.67885448
2002	3.47631406
2003	3.18252875
2004	3.69456842
2005	4.69434828
2006	6.01510882
2007	6.73109971
2008	6.75496843
2009	6.96009233
2010	7.38344428
2011	6.49063607
2012	5.09954339
2013	4.75741181
2014	6.1967865
2015	6.10500377
2016	5.83321502
2017	6.14845722
2018	5.53632542
2019	5.40191091
2020	6.2990483
2021	6.99047258