Year	current US$
2000	2.54414033
2001	2.846298
2002	2.01087168
2003	1.58256257
2004	1.72904167
2005	1.93634493
2006	2.32330826
2007	2.57683146
2008	2.76163179
2009	2.50572117
2010	2.99260099
2011	3.08231231
2012	3.07975495
2013	3.21439658
2014	3.16848585
2015	2.93572398
2016	2.96719366
2017	2.992478
2018	3.42177282
2019	3.81970465
2020	3.72824673
2021	3.87043524