Quarter	Millions of US Dollars
1977-01-01	42
1982-01-01	-43
1989-07-01	175
1990-10-01	82
1992-04-01	-4
1993-04-01	234
1995-07-01	250
1995-10-01	25
1996-01-01	150
1996-07-01	275
1997-04-01	500
1998-10-01	-138
1999-04-01	170
2000-01-01	-20
2000-07-01	-150
2001-04-01	875
2001-07-01	-75
2002-07-01	230
2004-01-01	1678
2004-04-01	-18
2004-10-01	1100
2005-01-01	1075
2005-04-01	2000
2005-07-01	1105
2005-10-01	2759
2006-01-01	5382
2006-04-01	3068
2006-07-01	2174
2006-10-01	12322
2007-01-01	6472
2007-04-01	1757
2007-07-01	6025
2007-10-01	6554
2008-01-01	118
2008-04-01	6827
2008-07-01	5593
2008-10-01	-3758
2009-01-01	-1866
2009-04-01	10535
2009-07-01	7639
2009-10-01	1302
2010-01-01	-1246
2010-04-01	-1798
2010-07-01	2002
2010-10-01	4990
2011-01-01	4860
2011-04-01	2904
2011-07-01	-885
2011-10-01	6627
2012-01-01	3729
2012-04-01	-1137
2012-07-01	2951
2012-10-01	5389
2013-01-01	7911
2013-04-01	892
2013-07-01	589
2013-10-01	1650
2014-01-01	-412
2014-04-01	6261
2014-07-01	-3148
2014-10-01	-352
2015-01-01	6060
2015-04-01	3717
2015-07-01	1523
2015-10-01	-1548
2016-01-01	1205
2016-04-01	13733
2016-07-01	3196
2016-10-01	4438
2017-01-01	-2748
2017-04-01	2460
2017-07-01	-2825
2017-10-01	13191
2018-01-01	2722
2018-04-01	-126