Year	current US$
2000	9.44474337
2001	8.0168126
2002	6.98155055
2003	10.3546946
2004	12.88149826
2005	14.15193855
2006	14.67563467
2007	15.58643304
2008	14.98821687
2009	15.71497722
2010	19.88406768
2011	21.8699175
2012	20.96688033
2013	18.14890621
2014	17.07695483
2015	16.2194632
2016	14.32380354
2017	18.09694705
2018	18.85979432
2019	16.79817887
2020	15.61540863
2021	16.12019148