Year	current US$
2000	21.80707195
2001	20.58261
2002	21.22306824
2003	22.73983446
2004	25.06913403
2005	26.75295884
2006	22.81492161
2007	21.08117607
2008	19.50283739
2009	17.75764996
2010	15.63227536
2011	16.49165881
2012	15.31682981
2013	17.69034904
2014	17.790032
2015	13.61935769
2016	15.19718005
2017	17.18898718
2018	17.12662443
2019	18.0562148
2020	18.83323712
2021	21.69177254