Quarter	Millions of US Dollars
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	0
1978-10-01	0
1979-01-01	35
1979-04-01	35
1979-07-01	35
1979-10-01	51
1980-01-01	14
1980-04-01	16
1980-07-01	15
1980-10-01	0
1981-01-01	68
1981-04-01	137
1981-07-01	254
1981-10-01	298
1982-01-01	261
1982-04-01	210
1982-07-01	141
1982-10-01	251
1983-01-01	217
1983-04-01	226
1983-07-01	340
1983-10-01	197
1984-01-01	204
1984-04-01	182
1984-07-01	56
1984-10-01	367
1985-01-01	374
1985-04-01	450
1985-07-01	484
1985-10-01	420
1986-01-01	602
1986-04-01	585
1986-07-01	737
1986-10-01	714
1987-01-01	596
1987-04-01	793
1987-07-01	1110
1987-10-01	1206
1988-01-01	1165
1988-04-01	950
1988-07-01	599
1988-10-01	402
1989-01-01	576
1989-04-01	462
1989-07-01	327
1989-10-01	255
1990-01-01	1005
1990-04-01	1025
1990-07-01	1029
1990-10-01	1137
1991-01-01	324
1991-04-01	515
1991-07-01	750
1991-10-01	1130
1992-01-01	1478
1992-04-01	1334
1992-07-01	1860
1992-10-01	1811
1993-01-01	1348
1993-04-01	1609
1993-07-01	3855
1993-10-01	4195
1994-01-01	5628
1994-04-01	5677
1994-07-01	5721
1994-10-01	4582
1995-01-01	2905
1995-04-01	3716
1995-07-01	5862
1995-10-01	7336
1996-01-01	8243
1996-04-01	8070
1996-07-01	6591
1996-10-01	6732
1997-01-01	6936
1997-04-01	8047
1997-07-01	8538
1997-10-01	7879
1998-01-01	8435
1998-04-01	7483
1998-07-01	5677
1998-10-01	6226
1999-01-01	4435
1999-04-01	4404
1999-07-01	4731
1999-10-01	5016
2000-01-01	5358
2000-04-01	6725
2000-07-01	6764
2000-10-01	5696
2001-01-01	6969
2001-04-01	7905
2001-07-01	8391
2001-10-01	9353
2002-01-01	8785
2002-04-01	8966
2002-07-01	8776
2002-10-01	8781
2003-01-01	9411
2003-04-01	11310
2003-07-01	12380
2003-10-01	14262
2004-01-01	13609
2004-04-01	11570
2004-07-01	10282
2004-10-01	7113
2005-01-01	6191
2005-04-01	4443
2005-07-01	4449
2005-10-01	5383
2006-01-01	5886
2006-04-01	7218
2006-07-01	8503
2006-10-01	7975
2007-01-01	7105
2007-04-01	7558
2007-07-01	7344
2007-10-01	9490
2008-01-01	10519
2008-04-01	8955
2008-07-01	8115
2008-10-01	6001
2009-01-01	4827
2009-04-01	3355
2009-07-01	3077
2009-10-01	4605
2010-01-01	7467
2010-04-01	7536
2010-07-01	9598
2010-10-01	6367
2011-01-01	6566
2011-04-01	8338
2011-07-01	5253
2011-10-01	6483
2012-01-01	4637
2012-04-01	4178
2012-07-01	8381
2012-10-01	8152
2013-01-01	11027
2013-04-01	13095
2013-07-01	9961
2013-10-01	12603
2014-01-01	16025
2014-04-01	15266
2014-07-01	14332
2014-10-01	12613
2015-01-01	8475
2015-04-01	8084
2015-07-01	12458
2015-10-01	14006
2016-01-01	17328
2016-04-01	22528
2016-07-01	18091
2016-10-01	22247
2017-01-01	20616
2017-04-01	21931
2017-07-01	24817
2017-10-01	17794
2018-01-01	16020
2018-04-01	12104