Quarter	Millions of US Dollars
1997-07-01	150
1997-10-01	150
1998-01-01	300
1998-04-01	469
1998-07-01	475
1998-10-01	475
1999-01-01	469
1999-04-01	366
1999-07-01	368
1999-10-01	364
2000-01-01	361
2000-04-01	361
2000-07-01	206
2000-10-01	209
2001-01-01	56
2001-10-01	150
2002-01-01	675
2002-04-01	1275
2002-07-01	1275
2002-10-01	2905
2003-01-01	4955
2003-04-01	5105
2003-07-01	5105
2003-10-01	5130
2004-01-01	5585
2004-04-01	6360
2004-07-01	6560
2004-10-01	6830
2005-01-01	7130
2005-04-01	6880
2005-07-01	6850
2005-10-01	6810
2006-01-01	6662
2006-04-01	7079
2006-07-01	7354
2006-10-01	7936
2007-01-01	9317
2007-04-01	11233
2007-07-01	11481
2007-10-01	11009
2008-01-01	11131
2008-04-01	12767
2008-07-01	16118
2008-10-01	16043
2009-01-01	15098
2009-04-01	17537
2009-07-01	17325
2009-10-01	16771
2010-01-01	16751
2010-04-01	18882
2010-07-01	18857
2010-10-01	19923
2011-01-01	23623
2011-04-01	23938
2011-07-01	23600
2011-10-01	23649
2012-01-01	23506
2012-04-01	23394
2012-07-01	26317
2012-10-01	29727
2013-01-01	31990
2013-04-01	36906
2013-07-01	35267
2013-10-01	37208
2014-01-01	36457
2014-04-01	36191
2014-07-01	35413
2014-10-01	35238
2015-01-01	34491
2015-04-01	34785
2015-07-01	34495
2015-10-01	34250
2016-01-01	33909
2016-04-01	33515
2016-07-01	33133
2016-10-01	34604
2017-01-01	33814
2017-04-01	33757
2017-07-01	34227
2017-10-01	33756
2018-01-01	32458
2018-04-01	29501