Year	current US$
1991	3440
1992	3090
1993	2920
1994	2650
1995	2640
1996	2600
1997	2650
1998	2130
1999	1750
2000	1710
2001	1780
2002	2100
2003	2590
2004	3410
2005	4450
2006	5810
2007	7560
2008	9580
2009	9230
2010	9980
2011	11060
2012	13470
2013	15160
2014	14590
2015	11740
2016	9680
2017	9160
2018	10180
2019	11190
2020	10660
2021	11720
2022	12810
2023	14250