Quarter	Millions of US Dollars
1987-07-01	120
1987-10-01	-1934
1988-01-01	394
1988-04-01	756
1988-07-01	1321
1988-10-01	2002
1989-01-01	-347
1989-04-01	8544
1989-07-01	727
1989-10-01	-1129
1990-01-01	6104
1990-04-01	-1577
1990-07-01	-596
1990-10-01	-5888
1991-01-01	-1014
1991-04-01	3769
1991-07-01	-2045
1991-10-01	-428
1992-01-01	-1464
1992-04-01	2774
1992-07-01	3018
1992-10-01	2021
1993-01-01	510
1993-04-01	2410
1993-07-01	-5028
1993-10-01	-1624
1994-01-01	-1197
1994-04-01	-1367
1994-07-01	2776
1994-10-01	2787
1995-01-01	-846
1995-04-01	1097
1995-07-01	-734
1995-10-01	1949
1996-01-01	-1685
1996-04-01	-366
1996-07-01	-881
1996-10-01	234
1997-01-01	313
1997-04-01	-729
1997-07-01	3474
1997-10-01	5137
1998-01-01	-1342
1998-04-01	725
1998-07-01	1637
1998-10-01	-2431
1999-01-01	-1978
1999-04-01	-3389
1999-07-01	-1018
1999-10-01	1983
2000-01-01	-1952
2000-04-01	1292
2000-07-01	568
2000-10-01	3341
2001-01-01	-497
2001-04-01	-348
2001-07-01	-166
2001-10-01	-614
2002-01-01	398
2002-04-01	776
2002-07-01	457
2002-10-01	1243
2003-01-01	-554
2003-04-01	1231
2003-07-01	1529
2003-10-01	4592
2004-01-01	1291
2004-04-01	2253
2004-07-01	848
2004-10-01	3267
2005-01-01	-1042
2005-04-01	2773
2005-07-01	-728
2005-10-01	1142
2006-01-01	2012
2006-04-01	2062
2006-07-01	-2209
2006-10-01	891
2007-01-01	-160
2007-04-01	-265
2007-07-01	-2442
2007-10-01	-1001
2008-01-01	-3
2008-04-01	1393
2008-07-01	-458
2008-10-01	-3199
2009-01-01	-3208
2009-04-01	5
2009-07-01	-791
2009-10-01	1705
2010-01-01	-457
2010-04-01	1620
2010-07-01	-1359
2010-10-01	2452
2011-01-01	307
2011-04-01	1713
2011-07-01	1270
2011-10-01	791
2012-01-01	-677
2012-04-01	1917
2012-07-01	182
2012-10-01	1336
2013-01-01	-184
2013-04-01	426
2013-07-01	-629
2013-10-01	676
2014-01-01	-391
2014-04-01	3094
2014-07-01	-425
2014-10-01	4551
2015-01-01	383
2015-04-01	-6
2015-07-01	1981
2015-10-01	-827
2016-01-01	-756
2016-04-01	2432
2016-07-01	-1250
2016-10-01	-906
2017-01-01	1892
2017-04-01	952
2017-07-01	1204
2017-10-01	399
2018-01-01	998