Year	current US$
2000	5.847290255520024
2001	6.021917768231351
2002	5.874614532668015
2003	6.360221494495781
2004	8.313772348628875
2005	9.51687030435402
2006	9.93077011328906
2007	10.609498668439555
2008	11.419520945986244
2009	10.787847006319573
2010	11.902967530849352
2011	13.083789139187346
2012	16.167912145436237
2013	16.801997422628805
2014	17.778108224463043
2015	18.388591169271127
2016	16.384550897553606
2017	16.749658611667964
2018	17.036839431971924
2019	17.07137746390997
2020	18.838291960663025
2021	19.620036105387385