Year	current US$
2000	4.233630634870736
2001	4.103468422513142
2002	4.198447932846614
2003	4.003627861206612
2004	4.146490322744725
2005	5.7019042349965705
2006	5.759360760885599
2007	6.645841810369859
2008	8.199623917559954
2009	9.07480861436854
2010	10.724137113461547
2011	12.330608696178885
2012	12.539592644672975
2013	12.056662161239664
2014	12.161165230591461
2015	13.96984650801981
2016	15.011369421246057
2017	17.787044660082458
2018	18.646004766527035
2019	19.277549825392246
2020	21.022990212221202
2021	22.42794348877405