Quarter	Millions of US Dollars
1971-01-01	0
1971-04-01	0
1971-07-01	0
1971-10-01	0
1972-01-01	0
1972-04-01	0
1972-07-01	0
1972-10-01	0
1973-01-01	0
1973-04-01	0
1973-07-01	0
1973-10-01	0
1974-01-01	0
1974-04-01	0
1974-07-01	0
1974-10-01	0
1975-01-01	0
1975-04-01	0
1975-07-01	0
1975-10-01	23
1976-01-01	24
1976-04-01	24
1976-07-01	25
1976-10-01	0
1977-01-01	0
1977-04-01	4
1977-07-01	11
1977-10-01	12
1978-01-01	41
1978-04-01	44
1978-07-01	39
1978-10-01	40
1979-01-01	144
1979-04-01	388
1979-07-01	463
1979-10-01	548
1980-01-01	706
1980-04-01	1002
1980-07-01	1159
1980-10-01	1485
1981-01-01	1311
1981-04-01	985
1981-07-01	937
1981-10-01	1165
1982-01-01	1561
1982-04-01	1879
1982-07-01	2050
1982-10-01	1538
1983-01-01	1202
1983-04-01	896
1983-07-01	879
1983-10-01	1031
1984-01-01	1937
1984-04-01	2617
1984-07-01	4041
1984-10-01	7084
1985-01-01	8030
1985-04-01	8541
1985-07-01	9201
1985-10-01	7327
1986-01-01	7228
1986-04-01	7123
1986-07-01	6256
1986-10-01	5707
1987-01-01	4169
1987-04-01	3058
1987-07-01	4540
1987-10-01	5455
1988-01-01	5671
1988-04-01	6193
1988-07-01	4501
1988-10-01	4563
1989-01-01	5132
1989-04-01	5035
1989-07-01	4699
1989-10-01	5460
1990-01-01	5064
1990-04-01	6048
1990-07-01	7825
1990-10-01	7422
1991-01-01	8600
1991-04-01	10053
1991-07-01	11662
1991-10-01	13921
1992-01-01	13735
1992-04-01	16490
1992-07-01	16601
1992-10-01	16375
1993-01-01	16708
1993-04-01	15784
1993-07-01	21381
1993-10-01	20229
1994-01-01	20175
1994-04-01	18414
1994-07-01	19842
1994-10-01	21315
1995-01-01	24482
1995-04-01	25463
1995-07-01	23766
1995-10-01	25839
1996-01-01	24195
1996-04-01	29463
1996-07-01	24088
1996-10-01	27399
1997-01-01	26058
1997-04-01	23293
1997-07-01	24769
1997-10-01	26000
1998-01-01	32692
1998-04-01	32145
1998-07-01	37073
1998-10-01	40855
1999-01-01	32314
1999-04-01	33239
1999-07-01	34779
1999-10-01	34790
2000-01-01	38248
2000-04-01	40523
2000-07-01	40455
2000-10-01	50309
2001-01-01	63582
2001-04-01	58005
2001-07-01	64748
2001-10-01	58336
2002-01-01	52335
2002-04-01	69699
2002-07-01	69779
2002-10-01	75394
2003-01-01	84378
2003-04-01	93119
2003-07-01	100937
2003-10-01	108339
2004-01-01	108026
2004-04-01	110228
2004-07-01	117725
2004-10-01	126288
2005-01-01	118181
2005-04-01	112672
2005-07-01	126264
2005-10-01	122568
2006-01-01	132644
2006-04-01	142776
2006-07-01	135141
2006-10-01	151453
2007-01-01	155491
2007-04-01	177576
2007-07-01	171586
2007-10-01	207972
2008-01-01	254544
2008-04-01	266402
2008-07-01	251680
2008-10-01	225609
2009-01-01	199492
2009-04-01	233048
2009-07-01	229682
2009-10-01	243786
2010-01-01	255987
2010-04-01	238094
2010-07-01	275002
2010-10-01	263742
2011-01-01	314980
2011-04-01	303824
2011-07-01	281407
2011-10-01	279358
2012-01-01	293377
2012-04-01	267442
2012-07-01	285325
2012-10-01	272888
2013-01-01	278978
2013-04-01	301398
2013-07-01	316353
2013-10-01	334263
2014-01-01	326432
2014-04-01	318567
2014-07-01	307611
2014-10-01	273484
2015-01-01	265928
2015-04-01	259825
2015-07-01	236452
2015-10-01	220493
2016-01-01	259683
2016-04-01	265483
2016-07-01	280819
2016-10-01	276138
2017-01-01	270766
2017-04-01	255216
2017-07-01	250232
2017-10-01	254429
2018-01-01	258327
2018-04-01	246513