Quarter	Millions of US Dollars
1997-01-01	354
1997-04-01	58
1997-07-01	1635
1998-01-01	97
1998-10-01	-48
1999-01-01	333
1999-07-01	33
1999-10-01	236
2000-01-01	482
2000-07-01	376
2001-01-01	639
2001-07-01	212
2002-01-01	132
2002-04-01	268
2002-10-01	100
2003-01-01	541
2003-04-01	215
2004-01-01	336
2004-04-01	725
2004-07-01	-225
2004-10-01	-236
2005-01-01	-656
2006-01-01	-575
2006-07-01	-706
2006-10-01	192
2007-04-01	338
2007-07-01	68
2008-01-01	-660
2008-04-01	-239
2008-07-01	-42
2009-01-01	-690
2009-04-01	793
2009-07-01	-39
2009-10-01	1876
2010-01-01	-730
2010-07-01	1211
2011-01-01	265
2011-07-01	1073
2012-04-01	1893
2012-10-01	1089
2013-04-01	1500
2013-07-01	199
2013-10-01	1750
2014-04-01	477
2014-10-01	44
2015-01-01	834
2015-04-01	32
2015-07-01	21
2015-10-01	543
2016-04-01	15
2016-07-01	-143
2016-10-01	-193
2017-01-01	1334
2017-04-01	-1744
2017-07-01	-479
2017-10-01	1001
2018-04-01	877