Year	current US$
1972	3410
1973	4040
1974	5970
1975	9200
1976	13490
1977	12610
1978	14080
1979	17710
1980	18070
1981	19600
1982	17340
1983	15960
1984	15140
1985	13540
1986	15810
1987	14730
1988	13870
1989	16650
1990	16550
1991	12560
1992	16340
1993	18790
1994	18810
1995	19910
1996	19930
1997	20860
1998	19800
1999	17530
2000	19000
2001	19710
2002	19760
2003	23240
2004	29130
2005	35760
2006	42480
2007	47530
2008	51810
2009	45410
2010	43190
2011	44130
2012	49020
2013	51300
2014	50050
2015	41040
2016	34540
2017	30870
2018	32300
2019	35240
2020	32790
2021	35990
2022	40730
2023	46140