Quarter	Millions of US Dollars
1972-01-01	32
1972-04-01	32
1972-07-01	64
1972-10-01	64
1973-01-01	73
1973-04-01	79
1973-07-01	79
1973-10-01	73
1974-01-01	76
1974-04-01	74
1974-07-01	147
1974-10-01	158
1975-01-01	271
1975-04-01	411
1975-07-01	379
1975-10-01	422
1976-01-01	510
1976-04-01	700
1976-07-01	1021
1976-10-01	1232
1977-01-01	1224
1977-04-01	1236
1977-07-01	1606
1977-10-01	2019
1978-01-01	2663
1978-04-01	2921
1978-07-01	3421
1978-10-01	3701
1979-01-01	3909
1979-04-01	3911
1979-07-01	4002
1979-10-01	4077
1980-01-01	4054
1980-04-01	4287
1980-07-01	4263
1980-10-01	4158
1981-01-01	4048
1981-04-01	3893
1981-07-01	3980
1981-10-01	4415
1982-01-01	4079
1982-04-01	3996
1982-07-01	4341
1982-10-01	4862
1983-01-01	4829
1983-04-01	4514
1983-07-01	4852
1983-10-01	5195
1984-01-01	5366
1984-04-01	5156
1984-07-01	5077
1984-10-01	5327
1985-01-01	5562
1985-04-01	6053
1985-07-01	6859
1985-10-01	7718
1986-01-01	8912
1986-04-01	9510
1986-07-01	9831
1986-10-01	10691
1987-01-01	11635
1987-04-01	11896
1987-07-01	11995
1987-10-01	13121
1988-01-01	12681
1988-04-01	11878
1988-07-01	11676
1988-10-01	12101
1989-01-01	11805
1989-04-01	11409
1989-07-01	11611
1989-10-01	11085
1990-01-01	10747
1990-04-01	10882
1990-07-01	11069
1990-10-01	10316
1991-01-01	9574
1991-04-01	9001
1991-07-01	9488
1991-10-01	9510
1992-01-01	8949
1992-04-01	8982
1992-07-01	8224
1992-10-01	7230
1993-01-01	7017
1993-04-01	6627
1993-07-01	11866
1993-10-01	10990
1994-01-01	11552
1994-04-01	10231
1994-07-01	11270
1994-10-01	13944
1995-01-01	15198
1995-04-01	14738
1995-07-01	15755
1995-10-01	14373
1996-01-01	13071
1996-04-01	13912
1996-07-01	14454
1996-10-01	14589
1997-01-01	15239
1997-04-01	16642
1997-07-01	15092
1997-10-01	13163
1998-01-01	12181
1998-04-01	11302
1998-07-01	11296
1998-10-01	12526
1999-01-01	12592
1999-04-01	12035
1999-07-01	11400
1999-10-01	9955
2000-01-01	9176
2000-04-01	8044
2000-07-01	7888
2000-10-01	8122
2001-01-01	7402
2001-04-01	6684
2001-07-01	7184
2001-10-01	6282
2002-01-01	6981
2002-04-01	6407
2002-07-01	6253
2002-10-01	7436
2003-01-01	7250
2003-04-01	6961
2003-07-01	7192
2003-10-01	8572
2004-01-01	8552
2004-04-01	6824
2004-07-01	8647
2004-10-01	9031
2005-01-01	9678
2005-04-01	8975
2005-07-01	7418
2005-10-01	8896
2006-01-01	6702
2006-04-01	7398
2006-07-01	7076
2006-10-01	8443
2007-01-01	8460
2007-04-01	8703
2007-07-01	11078
2007-10-01	10664
2008-01-01	9542
2008-04-01	9171
2008-07-01	6955
2008-10-01	9292
2009-01-01	8265
2009-04-01	10413
2009-07-01	12397
2009-10-01	10223
2010-01-01	9597
2010-04-01	9721
2010-07-01	10466
2010-10-01	10242
2011-01-01	9976
2011-04-01	13260
2011-07-01	13505
2011-10-01	13412
2012-01-01	12135
2012-04-01	9438
2012-07-01	8559
2012-10-01	11682
2013-01-01	10324
2013-04-01	7360
2013-07-01	9371
2013-10-01	10172
2014-01-01	8189
2014-04-01	6216
2014-07-01	4345
2014-10-01	4296
2015-01-01	4838
2015-04-01	3291
2015-07-01	2931
2015-10-01	3780
2016-01-01	4148
2016-04-01	5298
2016-07-01	3729
2016-10-01	4485
2017-01-01	3852
2017-04-01	3669
2017-07-01	3302
2017-10-01	3603
2018-01-01	2959
2018-04-01	3637