Year	constant 2015 US$
1997	162.4062702863019
1998	155.90836505784313
1999	182.6379021852809
2000	181.1709991713496
2001	163.26069323215745
2002	152.6472702720583
2003	105.93421074858514
2004	130.95237148659194
2005	146.0595784861906
2006	161.91742122666017
2007	134.9078040498976
2008	136.474679984031
2009	139.62294775554903
2010	161.15214441952904
2011	155.4028787829938
2012	177.81394226444718
2013	184.94050586804585
2014	186.89412010794456
2015	208.08039188802093
2016	185.8970531291553
2017	184.1923647618117
2018	193.19977522469864
2019	194.41999152556284
2020	192.4824249923928
2021	188.82386057024527