Year	US Dollars, Monthly Level
1988-01-01	9344650512.859600
1989-01-01	10563557262.259100
1990-01-01	11430168453.588000
1991-01-01	11030368582.030602
1992-01-01	12244567208.206202
1993-01-01	13803340252.810701
1994-01-01	15889173339.993000
1995-01-01	17621614403.704998
1996-01-01	18726652621.912700
1997-01-01	20298065071.139600
1998-01-01	20628354229.915700
1999-01-01	22771910941.811100
2000-01-01	28370873347.388600
2001-01-01	25696245299.286600
2002-01-01	25656617164.249900
2003-01-01	27893391823.179000
2004-01-01	33819145336.014900
2005-01-01	36643199271.596100
2006-01-01	39702208014.959100
2007-01-01	45819962594.529800
2008-01-01	51318931868.285706
2009-01-01	42055228580.755806
2010-01-01	50837001137.414300
2011-01-01	58143972080.173904
2012-01-01	54008487621.520800
2013-01-01	56831372509.659195
2014-01-01	57536250839.514500
2015-01-01	53387793250.041800
2016-01-01	52252719440.530800
2017-01-01	53045228524.960900