Year	current US$
2000	4.0819268
2001	4.25561557
2002	4.63020075
2003	4.64879085
2004	4.91824894
2005	5.25099206
2006	5.20856708
2007	5.59686279
2008	5.81875373
2009	5.50430112
2010	5.61233762
2011	5.98265992
2012	6.25497093
2013	6.66659423
2014	6.56201295
2015	6.59479169
2016	6.94380331
2017	7.72156358
2018	8.03576355
2019	8.67839029
2020	8.19181798
2021	8.32342449