Year	current US$
2000	4.63975465
2001	4.95517566
2002	5.25802738
2003	6.69430656
2004	7.5287663
2005	7.80684267
2006	8.42607527
2007	9.58926813
2008	10.94352742
2009	10.76329548
2010	9.76146661
2011	11.09412364
2012	11.96715387
2013	7.59518764
2014	8.37618717
2015	8.64071276
2016	11.18498122
2017	15.59570326
2018	20.49283104
2019	20.55614454
2020	19.92490705
2021	21.02073564