Quarter	Millions of US Dollars
1988-04-01	18903
1988-07-01	17505
1988-10-01	17444
1989-01-01	16227
1989-04-01	14649
1989-07-01	15393
1989-10-01	16563
1990-01-01	16089
1990-04-01	16949
1990-07-01	18623
1990-10-01	17127
1991-01-01	17422
1991-04-01	16197
1991-07-01	17922
1991-10-01	17136
1992-01-01	17462
1992-04-01	17807
1992-07-01	17054
1992-10-01	15934
1993-01-01	16182
1993-04-01	14555
1993-07-01	11447
1993-10-01	11176
1994-01-01	10955
1994-04-01	10303
1994-07-01	10571
1994-10-01	11951
1995-01-01	10292
1995-04-01	10459
1995-07-01	10242
1995-10-01	10627
1996-01-01	12710
1996-04-01	14147
1996-07-01	14006
1996-10-01	14283
1997-01-01	13931
1997-04-01	13583
1997-07-01	13359
1997-10-01	13969
1998-01-01	14652
1998-04-01	12999
1998-07-01	12566
1998-10-01	12138
1999-01-01	14871
1999-04-01	16364
1999-07-01	16612
1999-10-01	17061
2000-01-01	18779
2000-04-01	19190
2000-07-01	17530
2000-10-01	20746
2001-01-01	17911
2001-04-01	18541
2001-07-01	18638
2001-10-01	20657
2002-01-01	22149
2002-04-01	25013
2002-07-01	23664
2002-10-01	25396
2003-01-01	28522
2003-04-01	32634
2003-07-01	29078
2003-10-01	33066
2004-01-01	33776
2004-04-01	32955
2004-07-01	35161
2004-10-01	37347
2005-01-01	38685
2005-04-01	37467
2005-07-01	36264
2005-10-01	39155
2006-01-01	39752
2006-04-01	41202
2006-07-01	41377
2006-10-01	45324
2007-01-01	46508
2007-04-01	48893
2007-07-01	46703
2007-10-01	43837
2008-01-01	44907
2008-04-01	45099
2008-07-01	37654
2008-10-01	30129
2009-01-01	30155
2009-04-01	34796
2009-07-01	37843
2009-10-01	38248
2010-01-01	38778
2010-04-01	35862
2010-07-01	41685
2010-10-01	42600
2011-01-01	44444
2011-04-01	45462
2011-07-01	41086
2011-10-01	42480
2012-01-01	46729
2012-04-01	47284
2012-07-01	49026
2012-10-01	51154
2013-01-01	52087
2013-04-01	45595
2013-07-01	47737
2013-10-01	46976
2014-01-01	49400
2014-04-01	50613
2014-07-01	45752
2014-10-01	43893
2015-01-01	42437
2015-04-01	43066
2015-07-01	39581
2015-10-01	39553
2016-01-01	42078
2016-04-01	40281
2016-07-01	40030
2016-10-01	36388
2017-01-01	38635
2017-04-01	40310
2017-07-01	43003
2017-10-01	42381
2018-01-01	42394