Year	current US$
1970	1.206065860298435
1971	1.3695879747743607
1972	1.503663942772266
1973	1.6263030479604057
1974	1.97996775493691
1975	1.5911383789374276
1976	1.366827497315393
1977	1.2845688658936238
1978	1.782519125743676
1979	2.149505936922344
1980	2.40734062731638
1981	2.5900372460179875
1982	2.399902633386944
1983	2.405085673033656
1984	2.4490726351464085
1985	2.4403645201181763
1986	2.9486175988467234
1987	3.43590078498323
1988	4.0048472811745865
1989	4.092067971022727
1990	4.502838862903235
1991	4.293281392571594
1992	5.715479375113712
1993	5.256061390134521
1994	5.315400320170178
1995	5.429675168090943
1996	4.396397708796434
1997	3.598701308256143
1998	4.4233228056954585
1999	5.125115307246144
2000	4.430078695407369
2001	3.7553082728318885
2002	3.5931184871464295
2003	3.4705703403970443
2004	3.3126797321491863
2005	4.554616803332094
2006	3.7284578048933805
2007	4.065810448948059
2008	3.904134895562814
2009	4.595526595717483
2010	4.489232223884849
2011	3.359713843570304
2012	4.0912790940299555
2013	5.609636925739017
2014	4.3060803858952745
2015	3.8052299123287203
2016	3.428746874302884
2017	3.6495993038617747
2018	3.609243966947033
2019	2.9726355616524276
2020	5.585653412453727
2021	4.356240063370873