Quarter	Millions of US Dollars
1997-01-01	31748
1997-04-01	36039
1997-07-01	37772
1997-10-01	38343
1998-01-01	38324
1998-04-01	38571
1998-07-01	38844
1998-10-01	38243
1999-01-01	40780
1999-04-01	38920
1999-07-01	42669
1999-10-01	41806
2000-01-01	41625
2000-04-01	40307
2000-07-01	40677
2000-10-01	40726
2001-01-01	40218
2001-04-01	40789
2001-07-01	39710
2001-10-01	37288
2002-01-01	37784
2002-04-01	39475
2002-07-01	39069
2002-10-01	39563
2003-01-01	40880
2003-04-01	40875
2003-07-01	41079
2003-10-01	41901
2004-01-01	42178
2004-04-01	43383
2004-07-01	45052
2004-10-01	46418
2005-01-01	49153
2005-04-01	50385
2005-07-01	50968
2005-10-01	51399
2006-01-01	50818
2006-04-01	52554
2006-07-01	52240
2006-10-01	52635
2007-01-01	52711
2007-04-01	55627
2007-07-01	55230
2007-10-01	55820
2008-01-01	53342
2008-04-01	51897
2008-07-01	53246
2008-10-01	51343
2009-01-01	51598
2009-04-01	49886
2009-07-01	50582
2009-10-01	50347
2010-01-01	52926
2010-04-01	53958
2010-07-01	60026
2010-10-01	66486
2011-01-01	70580
2011-04-01	83527
2011-07-01	87091
2011-10-01	91667
2012-01-01	106643
2012-04-01	110875
2012-07-01	120578
2012-10-01	122444
2013-01-01	127943
2013-04-01	139249
2013-07-01	143365
2013-10-01	152078
2014-01-01	163158
2014-04-01	173396
2014-07-01	183126
2014-10-01	185982
2015-01-01	194316
2015-04-01	195802
2015-07-01	184879
2015-10-01	202397
2016-01-01	194546
2016-04-01	195641
2016-07-01	207620
2016-10-01	211909
2017-01-01	222884
2017-04-01	237562
2017-07-01	246591
2017-10-01	263714
2018-01-01	268515