Year	current US$
1970	2.557585121142561
1971	2.782544657378613
1972	2.703775707742579
1973	4.0439224551871815
1974	5.4423140260418394
1975	7.556425489635797
1976	7.5198179282228805
1977	6.947467234187586
1978	7.770257331716981
1979	9.30754756854285
1980	10.739473673488838
1981	9.319874461483034
1982	8.649502485117534
1983	8.178368927279257
1984	7.916774936691893
1985	8.150684969795867
1986	9.136073272947078
1987	9.196402251329047
1988	9.200876840392716
1989	8.962100147651737
1990	12.749497767768979
1991	13.53125460195951
1992	11.814932273661642
1993	9.830785713296528
1994	10.610937185349398
1995	9.120382034556652
1996	9.3752048748928
1997	7.046136869957068
1998	7.426272367905835
1999	7.358837055117003
2000	6.573877341206284
2001	7.540774943171444
2002	7.368230438424785
2003	7.654645345819917
2004	7.610970741008506
2005	8.655890292240304
2006	8.335232758990658
2007	8.776988661430137
2008	10.667402247120613
2009	11.188813794774882
2010	11.871842933242483
2011	12.604839171306537
2012	11.867586702023633
2013	15.6886879689331
2014	14.819514759012124
2015	14.358832410268443
2016	15.90057815308499
2017	16.379335320069664
2018	17.624173118071592
2019	16.144658269415356
2020	18.774688588980112
2021	19.622900678373977