Quarter	Millions of US Dollars
1997-10-01	77531
1998-01-01	81639
1998-04-01	76848
1998-07-01	93280
1998-10-01	123128
1999-01-01	87535
1999-04-01	69015
1999-07-01	67761
1999-10-01	117552
2000-01-01	64337
2000-04-01	77450
2000-07-01	57084
2000-10-01	78538
2001-01-01	87727
2001-04-01	111187
2001-07-01	108703
2001-10-01	83570
2002-01-01	79258
2002-04-01	99962
2002-07-01	85399
2002-10-01	98161
2003-01-01	92910
2003-04-01	93109
2003-07-01	89676
2003-10-01	95788
2004-01-01	81296
2004-04-01	81153
2004-07-01	67899
2004-10-01	79644
2005-01-01	48735
2005-04-01	55906
2005-07-01	55708
2005-10-01	68386
2006-01-01	43813
2006-04-01	44014
2006-07-01	49756
2006-10-01	56159
2007-01-01	48009
2007-04-01	70833
2007-07-01	74949
2007-10-01	89394
2008-01-01	77017
2008-04-01	98117
2008-07-01	94820
2008-10-01	110450
2009-01-01	80209
2009-04-01	88142
2009-07-01	70250
2009-10-01	77229
2010-01-01	34905
2010-04-01	48990
2010-07-01	43622
2010-10-01	58883
2011-01-01	43163
2011-04-01	64707
2011-07-01	59181
2011-10-01	77572
2012-01-01	43327
2012-04-01	70810
2012-07-01	57092
2012-10-01	65114
2013-01-01	35293
2013-04-01	40791
2013-07-01	35747
2013-10-01	43489
2014-01-01	25436
2014-04-01	35139
2014-07-01	33028
2014-10-01	40152
2015-01-01	25999
2015-04-01	33312
2015-07-01	27126
2015-10-01	33208
2016-01-01	18552
2016-04-01	30026
2016-07-01	26618
2016-10-01	32909
2017-01-01	20016
2017-04-01	29996
2017-07-01	27175
2017-10-01	37322
2018-01-01	17498