Quarter	Millions of US Dollars
1988-04-01	13481
1988-07-01	13305
1988-10-01	16732
1989-01-01	15535
1989-04-01	10343
1989-07-01	13227
1989-10-01	17470
1990-01-01	18177
1990-04-01	8903
1990-07-01	13119
1990-10-01	16117
1991-01-01	17916
1991-04-01	12951
1991-07-01	17671
1991-10-01	20016
1992-01-01	20830
1992-04-01	16234
1992-07-01	16521
1992-10-01	19186
1993-01-01	17573
1993-04-01	15436
1993-07-01	14263
1993-10-01	15400
1994-01-01	17068
1994-04-01	16671
1994-07-01	19708
1994-10-01	21008
1995-01-01	16373
1995-04-01	14929
1995-07-01	17261
1995-10-01	14553
1996-01-01	17503
1996-04-01	14076
1996-07-01	16678
1996-10-01	16909
1997-01-01	16163
1997-04-01	11757
1997-07-01	13908
1997-10-01	12073
1998-01-01	12640
1998-04-01	8869
1998-07-01	10912
1998-10-01	9285
1999-01-01	11255
1999-04-01	9893
1999-07-01	11146
1999-10-01	11907
2000-01-01	9089
2000-04-01	6747
2000-07-01	6615
2000-10-01	4577
2001-01-01	4311
2001-04-01	3894
2001-07-01	5229
2001-10-01	5643
2002-01-01	6624
2002-04-01	4834
2002-07-01	7898
2002-10-01	6977
2003-01-01	5866
2003-04-01	4872
2003-07-01	6455
2003-10-01	6780
2004-01-01	6119
2004-04-01	4380
2004-07-01	4863
2004-10-01	5766
2005-01-01	4963
2005-04-01	4861
2005-07-01	6162
2005-10-01	5421
2006-01-01	4645
2006-04-01	3874
2006-07-01	5511
2006-10-01	6796
2007-01-01	5313
2007-04-01	5420
2007-07-01	9947
2007-10-01	9622
2008-01-01	8729
2008-04-01	8854
2008-07-01	9557
2008-10-01	9167
2009-01-01	11710
2009-04-01	23482
2009-07-01	20063
2009-10-01	24491
2010-01-01	21198
2010-04-01	19033
2010-07-01	24612
2010-10-01	28647
2011-01-01	28013
2011-04-01	30193
2011-07-01	23656
2011-10-01	25368
2012-01-01	29581
2012-04-01	27680
2012-07-01	31044
2012-10-01	36300
2013-01-01	28562
2013-04-01	18375
2013-07-01	21154
2013-10-01	18219
2014-01-01	9959
2014-04-01	16364
2014-07-01	20840
2014-10-01	24227
2015-01-01	21494
2015-04-01	18379
2015-07-01	22621
2015-10-01	19849
2016-01-01	21147
2016-04-01	17161
2016-07-01	17802
2016-10-01	15653
2017-01-01	16266
2017-04-01	13552
2017-07-01	14813
2017-10-01	13872
2018-01-01	15468