Year	current US$
2000	6.641955507743174
2001	6.58507871572777
2002	6.578338949704009
2003	6.737897679385009
2004	7.454482561422369
2005	9.353553318368357
2006	10.4127043260689
2007	11.900412710843758
2008	14.519558053396766
2009	15.413409017067522
2010	17.131367795162916
2011	19.356660636187
2012	20.489543384846414
2013	20.7581321273997
2014	21.51307500739654
2015	22.680126697923598
2016	22.587727838929027
2017	24.416081566057194
2018	25.384046712497124
2019	26.796378663934465
2020	28.766548708522233
2021	31.283896399417056