Year	constant 2010 US$
1991	430.294580849517
1992	411.618030850621
1993	393.871316543705
1994	369.797883003994
1995	398.6614931309
1996	399.572211815259
1997	370.78749605726
1998	355.140286182645
1999	352.470256763061
2000	307.41177907418
2001	290.74836829957
2002	274.555312059928
2003	270.358533174101
2004	267.030340454215
2005	261.926801421613
2006	274.285084830949
2007	278.756324817713
2008	281.165667077556
2009	286.353744577023
2010	292.447193667214
2011	300.342808408188
2012	309.101127378484
2013	314.111018434657
2014	320.08619146462
2015	327.064305298999
2016	327.971677081943
2017	322.29534744585
2018	317.955985399432