Year	current US$
2000	8.95671749
2001	9.59174156
2002	10.75085354
2003	12.44939899
2004	13.95743465
2005	18.53794861
2006	19.78735733
2007	20.83684349
2008	24.71139526
2009	24.40502357
2010	23.33815765
2011	24.68768311
2012	22.56604767
2013	24.43749619
2014	24.89271736
2015	25.72568893
2016	22.42886543
2017	28.69141388
2018	30.08619118
2019	31.21994209
2020	34.85019302
2021	34.34204865