Year	current US$
1970	2.6713665733976666
1971	3.284340769119628
1972	4.394980824128523
1973	6.02223185170843
1974	9.23873666518765
1975	11.989602003838586
1976	10.049278096827656
1977	12.077522575619358
1978	15.396350672236865
1979	18.75408386420799
1980	21.382327405281327
1981	19.78636749862366
1982	20.347480149004085
1983	18.466362373039694
1984	18.457390858681457
1985	20.091610048522973
1986	23.630542705339938
1987	26.805569086480233
1988	27.454483376769574
1989	26.919571225848916
1990	31.21556018043648
1991	30.09647577506798
1992	30.375935951738736
1993	26.779177200548222
1994	28.11777265410067
1995	28.03084887253511
1996	22.159218620899125
1997	20.268778787812064
1998	19.1860429819795
1999	18.426374360262162
2000	18.149195714434924
2001	20.109374749497412
2002	24.86851996712344
2003	33.33566229685029
2004	34.608553344889074
2005	34.05274632971752
2006	36.85412113102575
2007	43.453600813551745
2008	47.59854960620678
2009	48.12217048797078
2010	51.60173017400306
2011	51.479746689536505
2012	48.61524430206377
2013	52.749826424000986
2014	47.21650607086849
2015	45.47094663644758
2016	44.5445555433159
2017	48.90972295507498
2018	52.99065296507899
2019	50.58856181065865
2020	60.07473032320834
2021	55.36481037595187