Year	current US$
1970	2.472095304502636
1971	2.0762458631964984
1972	2.092185959210088
1973	2.145654966015265
1974	2.349014649849037
1975	2.8039205746661073
1976	2.6005513957430706
1977	2.425959546602313
1978	3.099435290288687
1979	3.8152828155678553
1980	4.441987419482279
1981	4.9658539264014605
1982	5.309693602920421
1983	5.629818752282072
1984	5.9647448766720945
1985	6.750052240705771
1986	7.394032717915882
1987	8.715916760112897
1988	8.67456636807486
1989	9.449117070812347
1990	10.284019948108329
1991	11.765602241440265
1992	10.482575843785447
1993	10.21772804530332
1994	10.574766551655244
1995	11.515202153058906
1996	10.591247456302666
1997	8.570259875635855
1998	8.123315950431222
1999	8.881644786042825
2000	7.0363421636805485
2001	9.443526934972995
2002	8.212165167758252
2003	9.509898351215016
2004	9.901516409747348
2005	9.870826947135416
2006	11.02482815720262
2007	9.84613662605517
2008	12.278229310330511
2009	12.407523022796465
2010	14.100617739754092
2011	14.409288675647787
2012	13.088030697367543
2013	12.81067602675867
2014	12.573184525892017
2015	12.263246850956453
2016	11.409032387783483
2017	10.306945198287593
2018	12.846916473777103
2019	10.688878126652364
2020	15.44186000015184
2021	15.063836673894317