Year	current US$
2000	16.21247856
2001	16.60871251
2002	16.61253898
2003	16.37850458
2004	16.02970807
2005	16.45849206
2006	17.0948198
2007	17.21057842
2008	16.19920746
2009	15.73677181
2010	15.36012187
2011	15.80896876
2012	15.92242175
2013	15.35696903
2014	15.90302354
2015	16.26495602
2016	17.13700515
2017	18.16563959
2018	19.87274273
2019	20.60840803
2020	17.68381057
2021	18.8658276