Quarter	Millions of US Dollars
1988-07-01	4125
1988-10-01	187
1989-01-01	6781
1989-04-01	5978
1989-07-01	5218
1989-10-01	-636
1990-01-01	-565
1990-04-01	3013
1990-07-01	3868
1990-10-01	-1702
1991-01-01	4397
1991-04-01	-101
1991-07-01	-4573
1991-10-01	-2471
1992-01-01	2139
1992-04-01	944
1992-07-01	-784
1992-10-01	-1500
1993-01-01	-1657
1993-04-01	-2444
1993-07-01	-1281
1993-10-01	56
1994-01-01	3383
1994-04-01	-29
1994-07-01	273
1994-10-01	1452
1995-01-01	2918
1995-04-01	-1525
1995-07-01	5270
1995-10-01	4453
1996-01-01	3008
1996-04-01	1947
1996-07-01	1432
1996-10-01	5934
1997-01-01	-184
1997-04-01	5170
1997-07-01	3887
1997-10-01	1583
1998-01-01	1042
1998-04-01	7697
1998-07-01	4268
1998-10-01	7392
1999-01-01	4130
1999-04-01	5719
1999-07-01	6755
1999-10-01	6099
2000-01-01	4283
2000-04-01	1563
2000-07-01	738
2000-10-01	-1891
2001-01-01	4688
2001-04-01	721
2001-07-01	1272
2001-10-01	6512
2002-01-01	5159
2002-04-01	1719
2002-07-01	7234
2002-10-01	-1944
2003-01-01	4040
2003-04-01	8535
2003-07-01	8331
2003-10-01	12781
2004-01-01	14733
2004-04-01	3524
2004-07-01	11820
2004-10-01	14781
2005-01-01	15175
2005-04-01	10155
2005-07-01	2933
2005-10-01	14290
2006-01-01	10103
2006-04-01	21171
2006-07-01	11362
2006-10-01	13158
2007-01-01	12540
2007-04-01	30056
2007-07-01	80567
2007-10-01	51123
2008-01-01	28935
2008-04-01	32903
2008-07-01	7377
2008-10-01	47354
2009-01-01	-30889
2009-04-01	-11829
2009-07-01	-1466
2009-10-01	-6013
2010-01-01	-27342
2010-04-01	-8325
2010-07-01	-5662
2010-10-01	15555
2011-01-01	-11366
2011-04-01	7741
2011-07-01	18591
2011-10-01	-5882
2012-01-01	41557
2012-04-01	-4096
2012-07-01	8833
2012-10-01	-24390
2013-01-01	-15023
2013-04-01	13743
2013-07-01	-6734
2013-10-01	12329
2014-01-01	13932
2014-04-01	22671
2014-07-01	21430
2014-10-01	25254
2015-01-01	8230
2015-04-01	3560
2015-07-01	2282
2015-10-01	4835
2016-01-01	9744
2016-04-01	4231
2016-07-01	1317
2016-10-01	-10742
2017-01-01	9899
2017-04-01	-11170
2017-07-01	-7928
2017-10-01	6141
2018-01-01	8974