Year	current US$
1997	2600
1998	2860
1999	2980
2000	3210
2001	3450
2002	3820
2003	4700
2004	6010
2005	7560
2006	8800
2007	10600
2008	12680
2009	12460
2010	12570
2011	13320
2012	14100
2013	15340
2014	16070
2015	15190
2016	14890
2017	15280
2018	17470
2019	19090
2020	19700
2021	21850
2022	23860
2023	24820