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	0
1976-01-01	0
1976-04-01	0
1976-07-01	0
1976-10-01	0
1977-01-01	0
1977-04-01	0
1977-07-01	0
1977-10-01	0
1978-01-01	0
1978-04-01	0
1978-07-01	19
1978-10-01	46
1979-01-01	68
1979-04-01	200
1979-07-01	192
1979-10-01	161
1980-01-01	232
1980-04-01	108
1980-07-01	108
1980-10-01	108
1981-01-01	0
1981-04-01	0
1981-07-01	15
1981-10-01	15
1982-01-01	15
1982-04-01	56
1982-07-01	40
1982-10-01	42
1983-01-01	41
1983-04-01	0
1983-07-01	30
1983-10-01	30
1984-01-01	30
1984-04-01	30
1984-07-01	37
1984-10-01	489
1985-01-01	654
1985-04-01	805
1985-07-01	773
1985-10-01	855
1986-01-01	708
1986-04-01	711
1986-07-01	755
1986-10-01	464
1987-01-01	678
1987-04-01	744
1987-07-01	768
1987-10-01	586
1988-01-01	358
1988-04-01	346
1988-07-01	802
1988-10-01	1008
1989-01-01	1254
1989-04-01	1691
1989-07-01	1317
1989-10-01	1444
1990-01-01	1439
1990-04-01	1075
1990-07-01	998
1990-10-01	1208
1991-01-01	964
1991-04-01	1087
1991-07-01	1360
1991-10-01	1386
1992-01-01	1652
1992-04-01	1626
1992-07-01	2209
1992-10-01	2686
1993-01-01	2863
1993-04-01	3655
1993-07-01	4428
1993-10-01	4017
1994-01-01	4148
1994-04-01	3329
1994-07-01	3233
1994-10-01	3164
1995-01-01	5469
1995-04-01	6955
1995-07-01	7046
1995-10-01	6924
1996-01-01	8097
1996-04-01	8886
1996-07-01	7908
1996-10-01	11126
1997-01-01	12296
1997-04-01	16000
1997-07-01	15347
1997-10-01	15344
1998-01-01	15404
1998-04-01	14979
1998-07-01	16461
1998-10-01	16678
1999-01-01	18673
1999-04-01	18475
1999-07-01	20800
1999-10-01	20335
2000-01-01	20236
2000-04-01	22856
2000-07-01	22139
2000-10-01	28377
2001-01-01	27374
2001-04-01	27204
2001-07-01	22994
2001-10-01	21241
2002-01-01	18171
2002-04-01	22020
2002-07-01	20779
2002-10-01	24379
2003-01-01	26012
2003-04-01	25079
2003-07-01	25772
2003-10-01	26417
2004-01-01	32995
2004-04-01	39716
2004-07-01	44354
2004-10-01	58190
2005-01-01	61569
2005-04-01	62633
2005-07-01	70408
2005-10-01	73225
2006-01-01	75589
2006-04-01	76267
2006-07-01	70687
2006-10-01	79047
2007-01-01	81983
2007-04-01	71022
2007-07-01	87479
2007-10-01	79743
2008-01-01	93320
2008-04-01	99632
2008-07-01	83735
2008-10-01	61237
2009-01-01	62007
2009-04-01	71850
2009-07-01	70603
2009-10-01	68486
2010-01-01	64454
2010-04-01	63816
2010-07-01	59233
2010-10-01	53438
2011-01-01	64430
2011-04-01	65981
2011-07-01	74010
2011-10-01	62141
2012-01-01	69293
2012-04-01	64587
2012-07-01	77193
2012-10-01	82075
2013-01-01	66126
2013-04-01	66823
2013-07-01	51399
2013-10-01	54574
2014-01-01	66297
2014-04-01	72231
2014-07-01	79326
2014-10-01	74932
2015-01-01	66425
2015-04-01	66609
2015-07-01	71106
2015-10-01	64787
2016-01-01	77464
2016-04-01	88560
2016-07-01	84509
2016-10-01	94793
2017-01-01	75459
2017-04-01	77234
2017-07-01	68049
2017-10-01	70469
2018-01-01	78361
2018-04-01	66773