Quarter	Millions of US Dollars
1997-04-01	344
1997-07-01	340
1997-10-01	335
1998-01-01	325
1998-04-01	332
1998-07-01	358
1998-10-01	358
1999-01-01	330
1999-04-01	317
1999-07-01	327
1999-10-01	308
2000-01-01	293
2000-04-01	293
2000-07-01	269
2000-10-01	565
2001-01-01	668
2001-04-01	1151
2001-07-01	1239
2001-10-01	1196
2002-01-01	1184
2002-04-01	1746
2002-07-01	1725
2002-10-01	1835
2003-01-01	1907
2003-04-01	2000
2003-07-01	2855
2003-10-01	2905
2004-01-01	2812
2004-04-01	2796
2004-07-01	2854
2004-10-01	3133
2005-01-01	2982
2005-04-01	3386
2005-07-01	3372
2005-10-01	2949
2006-01-01	3026
2006-04-01	3178
2006-07-01	3165
2006-10-01	3293
2007-01-01	3330
2007-04-01	3376
2007-07-01	3545
2007-10-01	3680
2008-01-01	3953
2008-04-01	4177
2008-07-01	3790
2008-10-01	3688
2009-01-01	3527
2009-04-01	3746
2009-07-01	3880
2009-10-01	3818
2010-01-01	4920
2010-04-01	4479
2010-07-01	4026
2010-10-01	3942
2011-01-01	4191
2011-04-01	6432
2011-07-01	6009
2011-10-01	5758
2012-01-01	9199
2012-04-01	7977
2012-07-01	9074
2012-10-01	11172
2013-01-01	12438
2013-04-01	12603
2013-07-01	14884
2013-10-01	16478
2014-01-01	18475
2014-04-01	20072
2014-07-01	19024
2014-10-01	20414
2015-01-01	17783
2015-04-01	17665
2015-07-01	19673
2015-10-01	20181
2016-01-01	21273
2016-04-01	21469
2016-07-01	21541
2016-10-01	22907
2017-01-01	23109
2017-04-01	25557
2017-07-01	26117
2017-10-01	27588
2018-01-01	30582
2018-04-01	27517