Year	current US$
2000	8.40154972
2001	7.82960544
2002	6.82008835
2003	7.25081179
2004	7.65156472
2005	7.26139203
2006	7.74529317
2007	8.1129448
2008	6.58189282
2009	10.44891432
2010	11.83937288
2011	12.12187806
2012	13.63477495
2013	14.39276023
2014	16.48761103
2015	11.29375554
2016	13.74954393
2017	10.01899996
2018	11.74335157
2019	11.63539512
2020	11.57365143
2021	12.55499103