Year	current US$
1988	9840
1989	11110
1990	11570
1991	12560
1992	13610
1993	14640
1994	16060
1995	16930
1996	17150
1997	17980
1998	18230
1999	18320
2000	20390
2001	20510
2002	19290
2003	21120
2004	24010
2005	20380
2006	24870
2007	23390
2008	27580
2009	24930
2010	23390
2011	23400
2012	24440
2013	25500
2014	25520
2015	25320
2016	26200
2017	27960
2018	28910
2019	29450
2020	23340
2021	30180
2022	33410