Quarter	Millions of US Dollars
1998-01-01	123870
1998-04-01	60297
1998-07-01	72994
1998-10-01	-11005
1999-01-01	154992
1999-04-01	172128
1999-07-01	54565
1999-10-01	53116
2000-01-01	123864
2000-04-01	113892
2000-07-01	1150
2000-10-01	104024
2001-01-01	202267
2001-04-01	76902
2001-07-01	-60811
2001-10-01	11963
2002-01-01	90766
2002-04-01	154229
2002-07-01	6299
2002-10-01	12527
2003-01-01	186741
2003-04-01	120199
2003-07-01	-62442
2003-10-01	117383
2004-01-01	235613
2004-04-01	159648
2004-07-01	27878
2004-10-01	103339
2005-01-01	208054
2005-04-01	147193
2005-07-01	-65988
2005-10-01	46853
2006-01-01	-11821
2006-04-01	-13995
2006-07-01	73783
2006-10-01	24435
2007-01-01	19619
2007-04-01	-38156
2007-07-01	52033
2007-10-01	80137
2008-01-01	174278
2008-04-01	-58982
2008-07-01	1751
2008-10-01	194408
2009-01-01	-51835
2009-04-01	206870
2009-07-01	69611
2009-10-01	121114
2010-01-01	109990
2010-04-01	367602
2010-07-01	130376
2010-10-01	60867
2011-01-01	34101
2011-04-01	339841
2011-07-01	280255
2011-10-01	12446
2012-01-01	9312
2012-04-01	278602
2012-07-01	147303
2012-10-01	75289
2013-01-01	113959
2013-04-01	54854
2013-07-01	122955
2013-10-01	79233
2014-01-01	83147
2014-04-01	175311
2014-07-01	28635
2014-10-01	71194
2015-01-01	128265
2015-04-01	34752
2015-07-01	17233
2015-10-01	-33479
2016-01-01	292878
2016-04-01	305858
2016-07-01	-85746
2016-10-01	-120236
2017-01-01	-22147
2017-04-01	28484
2017-07-01	54879
2017-10-01	44516
2018-01-01	17205