Year	current US$
1970	1.8684223535253957
1971	2.1288745784417995
1972	1.705082132804552
1973	2.1127964326097075
1974	3.027201426076642
1975	4.519157853073237
1976	4.271286152904994
1977	3.1864269788060335
1978	3.675929774505597
1979	4.224769883159104
1980	5.707226039079282
1981	4.754611692340104
1982	4.651830980477591
1983	4.261455078378236
1984	4.036875714933872
1985	3.8409839066052927
1986	4.709610385853267
1987	4.530970998653797
1988	5.111885346726381
1989	5.028384743470631
1990	4.595970972171457
1991	6.1655292581627466
1992	4.996911851285248
1993	3.784281000330674
1994	4.908857907169375
1995	3.498497785579505
1996	3.4542749134442103
1997	3.0726285468457446
1998	3.167218820230408
1999	2.770483139352517
2000	2.5902211985683006
2001	3.8584699602120387
2002	4.368039454953384
2003	3.8088691026907973
2004	4.441773941772059
2005	5.850737157349146
2006	5.511724391088962
2007	6.805579552950012
2008	6.839305304213836
2009	8.329988652369103
2010	8.936011734333377
2011	9.910558572518108
2012	8.192763475029276
2013	8.010665348259288
2014	8.837863417354532
2015	8.783910505441444
2016	7.653936617738606
2017	8.195360761812752
2018	6.590853175749269
2019	7.978524813392416
2020	8.742626240703368
2021	9.187903307996077