Year	current US$
2000	22.85133326
2001	21.56823477
2002	22.36374683
2003	24.11897344
2004	26.54474147
2005	28.41273868
2006	24.88800176
2007	23.21435736
2008	22.35252666
2009	20.52610601
2010	17.61865691
2011	18.80290125
2012	17.70259056
2013	20.72122996
2014	20.12091285
2015	14.65899859
2016	17.2578465
2017	18.72985132
2018	19.98371846
2019	20.11309165
2020	21.76157296
2021	25.00515736