Year	US Dollars, Monthly Level
1988-01-01	5062614250.945730
1989-01-01	5435597201.798181
1990-01-01	6343367490.138090
1991-01-01	6295597800.637910
1992-01-01	6468406182.285410
1993-01-01	5876970926.326270
1994-01-01	6567502865.516570
1995-01-01	7833043701.722100
1996-01-01	7461935077.952010
1997-01-01	6961875753.683440
1998-01-01	7864103261.518850
1999-01-01	8131271233.012790
2000-01-01	8413059987.070721
2001-01-01	9766654752.613640
2002-01-01	10194279961.714800
2003-01-01	13315679891.145800
2004-01-01	16127150565.788100
2005-01-01	19028088239.548603
2006-01-01	23090485779.702198
2007-01-01	22951540092.833100
2008-01-01	25636434255.466400
2009-01-01	21187375674.775100
2010-01-01	18667125718.020798
2011-01-01	20806546536.565700
2012-01-01	18787567054.905700
2013-01-01	18501416538.933300
2014-01-01	19157608074.074703
2015-01-01	17089504176.389100
2016-01-01	15846826199.432300
2017-01-01	15874628104.141800