Quarter	Millions of US Dollars
1988-04-01	16163
1988-07-01	14956
1988-10-01	14490
1989-01-01	13573
1989-04-01	12145
1989-07-01	12754
1989-10-01	13584
1990-01-01	13164
1990-04-01	13612
1990-07-01	14070
1990-10-01	13150
1991-01-01	13729
1991-04-01	13614
1991-07-01	15160
1991-10-01	15317
1992-01-01	14939
1992-04-01	14931
1992-07-01	14067
1992-10-01	13120
1993-01-01	13238
1993-04-01	12158
1993-07-01	8171
1993-10-01	7787
1994-01-01	7184
1994-04-01	6576
1994-07-01	6490
1994-10-01	6713
1995-01-01	6337
1995-04-01	6107
1995-07-01	6029
1995-10-01	5127
1996-01-01	5673
1996-04-01	5903
1996-07-01	5893
1996-10-01	5921
1997-01-01	6295
1997-04-01	6375
1997-07-01	6682
1997-10-01	6231
1998-01-01	6649
1998-04-01	6333
1998-07-01	6310
1998-10-01	6529
1999-01-01	7751
1999-04-01	8739
1999-07-01	9159
1999-10-01	10242
2000-01-01	11032
2000-04-01	11806
2000-07-01	11439
2000-10-01	13721
2001-01-01	12160
2001-04-01	13595
2001-07-01	14185
2001-10-01	16111
2002-01-01	17158
2002-04-01	19103
2002-07-01	18277
2002-10-01	20439
2003-01-01	22881
2003-04-01	25526
2003-07-01	25450
2003-10-01	28475
2004-01-01	29203
2004-04-01	29038
2004-07-01	30724
2004-10-01	33144
2005-01-01	34135
2005-04-01	33087
2005-07-01	32320
2005-10-01	33629
2006-01-01	33317
2006-04-01	34998
2006-07-01	36597
2006-10-01	40832
2007-01-01	40406
2007-04-01	42122
2007-07-01	42428
2007-10-01	40131
2008-01-01	41354
2008-04-01	41950
2008-07-01	34786
2008-10-01	28703
2009-01-01	28746
2009-04-01	33594
2009-07-01	36517
2009-10-01	37069
2010-01-01	37041
2010-04-01	34626
2010-07-01	40575
2010-10-01	40780
2011-01-01	42936
2011-04-01	43916
2011-07-01	39642
2011-10-01	41115
2012-01-01	45417
2012-04-01	45925
2012-07-01	47322
2012-10-01	49536
2013-01-01	50365
2013-04-01	44327
2013-07-01	45910
2013-10-01	45437
2014-01-01	47628
2014-04-01	49104
2014-07-01	43902
2014-10-01	42288
2015-01-01	41030
2015-04-01	40697
2015-07-01	36968
2015-10-01	36777
2016-01-01	39077
2016-04-01	37393
2016-07-01	37046
2016-10-01	33570
2017-01-01	35821
2017-04-01	37409
2017-07-01	40218
2017-10-01	39263
2018-01-01	39105