Year	current US$
2000	39.57255747
2001	40.21639916
2002	41.82310362
2003	46.46779042
2004	47.37336091
2005	43.82966363
2006	40.81167671
2007	40.96926161
2008	45.05469812
2009	43.41877724
2010	42.12217124
2011	42.89556405
2012	39.32643489
2013	40.16791848
2014	40.5626137
2015	26.62539046
2016	26.56571052
2017	26.90900049
2018	27.88107144
2019	27.44159242
2020	27.24901264
2021	26.47920834