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	10
1979-01-01	85
1979-04-01	85
1979-07-01	85
1979-10-01	75
1980-01-01	50
1980-04-01	100
1980-07-01	100
1980-10-01	100
1981-01-01	65
1981-04-01	356
1981-07-01	358
1981-10-01	387
1982-01-01	756
1982-04-01	468
1982-07-01	460
1982-10-01	531
1983-01-01	244
1983-04-01	340
1983-07-01	475
1983-10-01	493
1984-01-01	559
1984-04-01	396
1984-07-01	284
1984-10-01	673
1985-01-01	587
1985-04-01	747
1985-07-01	816
1985-10-01	519
1986-01-01	773
1986-04-01	664
1986-07-01	746
1986-10-01	744
1987-01-01	554
1987-04-01	767
1987-07-01	991
1987-10-01	1171
1988-01-01	1313
1988-04-01	960
1988-07-01	664
1988-10-01	845
1989-01-01	550
1989-04-01	845
1989-07-01	999
1989-10-01	605
1990-01-01	683
1990-04-01	402
1990-07-01	225
1990-10-01	246
1991-01-01	157
1991-04-01	169
1991-07-01	176
1991-10-01	288
1992-01-01	485
1992-04-01	489
1992-07-01	605
1992-10-01	1013
1993-01-01	802
1993-04-01	918
1993-07-01	1339
1993-10-01	934
1994-01-01	1292
1994-04-01	1427
1994-07-01	2111
1994-10-01	1708
1995-01-01	1778
1995-04-01	3981
1995-07-01	4147
1995-10-01	4711
1996-01-01	4233
1996-04-01	3033
1996-07-01	9663
1996-10-01	11173
1997-01-01	10971
1997-04-01	11047
1997-07-01	4690
1997-10-01	26135
1998-01-01	25980
1998-04-01	26233
1998-07-01	25849
1998-10-01	3694
1999-01-01	4398
1999-04-01	11543
1999-07-01	12813
1999-10-01	15037
2000-01-01	17525
2000-04-01	47257
2000-07-01	50333
2000-10-01	57166
2001-01-01	55697
2001-04-01	20138
2001-07-01	19094
2001-10-01	10147
2002-01-01	21625
2002-04-01	28066
2002-07-01	31512
2002-10-01	32624
2003-01-01	22983
2003-04-01	20416
2003-07-01	18883
2003-10-01	18664
2004-01-01	17958
2004-04-01	54475
2004-07-01	59012
2004-10-01	62195
2005-01-01	65407
2005-04-01	36068
2005-07-01	29314
2005-10-01	28247
2006-01-01	27164
2006-04-01	12445
2006-07-01	14894
2006-10-01	14528
2007-01-01	17409
2007-04-01	17640
2007-07-01	14891
2007-10-01	20954
2008-01-01	15098
2008-04-01	19379
2008-07-01	17673
2008-10-01	11840
2009-01-01	15767
2009-04-01	11309
2009-07-01	14006
2009-10-01	13866
2010-01-01	10464
2010-04-01	10942
2010-07-01	12463
2010-10-01	11004
2011-01-01	12875
2011-04-01	10510
2011-07-01	8513
2011-10-01	8305
2012-01-01	6774
2012-04-01	9002
2012-07-01	9416
2012-10-01	9003
2013-01-01	8607
2013-04-01	6349
2013-07-01	6202
2013-10-01	12761
2014-01-01	16272
2014-04-01	18690
2014-07-01	21904
2014-10-01	18227
2015-01-01	14237
2015-04-01	12902
2015-07-01	11934
2015-10-01	9351
2016-01-01	12809
2016-04-01	32925
2016-07-01	29198
2016-10-01	33546
2017-01-01	31926
2017-04-01	12985
2017-07-01	14072
2017-10-01	9776
2018-01-01	8372
2018-04-01	11194